answer: 340 m/s
explanation: in this instance, the sound wave travels 340 meters in 1 second, so the speed of the wave is 340 m/s. remember, when there is a reflection, the wave doubles its distance. in other words, the distance traveled by the sound wave in 1 second is equivalent to the 170 meters down to the canyon wall plus the 170 meters back from the canyon wall.
The speed of the wave is 340 m/s. It can be calculated by dividing distance by time.
Given:
Distance = 170 meters
Time = 1 Seconds
What is Speed?It is defined as the ratio between distance and time.
Speed = Distance / Time
In this instance, The sound wave travels 340 meters in 1 second, So the speed of the wave is 340 m/s.
When there is a reflection, the wave doubles its distance. In other words, the distance traveled by the sound wave in 1 second is equivalent to 170 meters down to the canyon wall plus 170 meters back from the canyon wall.
Thus, the speed of the wave is 340 m/s.
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Monochromatic radiation of frequency greater than the threshold frequency is incident on a metal do all the electrons emitted by photoelectric emission have the same kinetic energy.
Yo sup??
No it isn't necessary that they will have the same Kinetic energy.
Hope this helps
What is the oscillation period of your eardrum when you are listening to the A4 note on a piano (frequency 440 Hz)?
The period is the inverse of the frequence:
[tex]T=\dfrac{1}{f}=\dfrac{1}{440}=0.0022\overline{72}[/tex]
Answer:
T = 0.002 s.
Explanation:
Given data:
Frequency, [tex]f = 440 \ \rm Hz[/tex]
The time period of oscillation of the eardrum can be expressed as,
[tex]T = \frac{1}{f}[/tex]
[tex]T = \frac{1}{440 \ \rm Hz}[/tex]
[tex]T = 0.002 \ s.[/tex]
Which motion maps show an object in uniform circular motion? Check all that apply.
V
W
X
Y
Z
Answer:
V, since all the directions are uniform
W, since all the directions are uniform
Y, since all the directions are uniform
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which statement below is FALSE? A Gravity acts on any object with mass. B The closer objects are, the stronger the gravitational force between them. C The farther you are from the center of the Earth, the less gravitational force you feel. D Gravitational force depends on what the object is made of.
Answer:
Explanation:
The answer is D. The gravitational force of an object does NOT depend on what the object is made of.
Gravitational force depends on what the object is made of is false.
Gravitational force is the force of attraction that acts on all matters.
The farther you are from the center of the Earth, the less gravitational force
you feel as the force is strongest at the center.
The closer objects are, the stronger the gravitational force between them as
it is a force of attraction between objects on earth. Gravity is however not
dependent on what objects are made of as it acts on all bodies present on
earth.
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How does the distance the Earth is from the Sun affect its orbit?
The force needed to lift an object is equal in size to the gravitational force on the object. How much work is done in lifting an object that has a mass of 5 kg a vertical distance of 2 m?
Answer:
Work done in lifting the object = 98 J
Explanation:
Work: Work can be defined as the product of force and distance.
The S.I unit of work is Joules (J).
Mathematically it can be expressed as
W = F × d................. Equation 1
Where W = work done, F = force needed to lift the object, d = distance
The gravitational force on the object = Weight of the object
Weight of the object = mg .................. Equation 2
Where m = mass of the object, g = acceleration due to gravity
Given: m = 5 kg,
Constant: g = 9.8 m/s²
Substituting these values into equation 2
Weight of the object = 5 × 9.8
Weight of the object = 49 N
Since weight of the object = force needed to lift the object,
F = 49 N
Also Given: d = 2 m
Substituting these values into equation 1
W = 49 × 2
W = 98 J
Work done in lifting the object = 98 J
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A circuit has a voltage drop of 24.0 V across a 30.0 resistor that carries a
current of 0.800 A. What is the power conducted by the resistor? Use P = VI.
O A. 19.2 W
O B. 1.25 W
O c. 24.0 W
O
D. 720.0 W
(A) 19.2 W
Explanation:
Given-
Voltage drop, V = 24 V
Resistor = 30Ω
Current, I = 0.8 A
Power, P = ?
We know,
P = VI
P = 24 (0.8)
P = 19.2 W
Therefore, the power conducted by the resistor is 19.2 W
Answer:
19.2
Explanation:
A ball is dropped from the top of a building.
When does the ball have the most kinetic energy?
Answer:
Right before it hits the ground.
Explanation:
It has the most kinetic energy at the very end of its descent when it is moving the fastest.
2. What is the speed (v) of a wave that has a wavelength (a)
of 2 m and a frequency (f) of 6 Hz?
Answer:12m/s
Explanation:
Frequency=6Hz
Wavelength=2m
Wave speed=frequency x Wavelength
Wave speed=6 x 2
Wave speed=12m/s
The speed of a wave with a frequency of 6 Hz and a wavelength of 2 m is 12 m/s.
Explanation:The speed (v) of a wave is calculated by the formula v = fλ, where 'f' is the frequency and 'λ' (lambda) is the wavelength. Given the frequency (f) of 6 Hz and a wavelength ('λ') of 2 m, we can compute the speed of the wave using this formula:
v = 6 Hz × 2 m = 12 m/s.
Therefore, the speed of the wave is 12 meters per second (12 m/s).
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Which products rely on the ability of ionic compounds to conduct electricity?
Cell phones and remote control toys are the products which rely on the ability of ionic compounds to conduct electricity.
Explanation:
Ionic compounds are those which are formed between electronegative and electropositive elements. So some of the electrons will be always free in these compounds. Among the options given in the question, cell phones and remote control toys are the products which uses ionic products. As most of the semiconducting compounds or electronic compounds are ionic in nature. And cell phones and remote control toys uses the movement of electrons from ionic compounds to do the work.
Thus, cell phones and remote control toys are the products which rely on the ability of ionic compounds to conduct electricity.
Answer:
(B) cell phones
Explanation:
jus took the quiz
How does the health of the air and atmosphere affect the biosphere? -
Answer:
Because of its involvement in the Earth's carbon cycle and nitrogen cycle, the biosphere influences the amounts of some of the major greenhouse gases such as methane, carbon dioxide, and nitrous oxide.
Answer:
The health of the air and atmosphere affects the biosphere because if the atmosphere/air turned poisonous or something between those lines, most of the living organisms would die. In other words, the damaged air would affect the biosphere.
Explanation:
*My answer is my explanation ._.*
A hydraulic lift is used to lift a heavy box that is pushing down on a 1.5-m2 piston with a force of 1,700 N. What force needs to be exerted on a 0.12-m2 piston to lift the box?
Answer:
136 N
Explanation:
Pressure on large piston = pressure on small piston
F₁ / A₁ = F₂ / A₂
1700 N / 1.5 m² = F / 0.12 m²
F = 136 N
How does Mercury's close proximity to the sun and thin atmosphere affect its ability to maintain liquid water
on its surface?
Answer
A thin atmosphere does not supply much oxygen, and the heat from the sun would evaporate it, because mercury is close to the sun.
Final answer:
Mercury's close proximity to the Sun and thin atmosphere prevent it from maintaining liquid water. Its lack of substantial atmosphere and the intense solar radiation lead to extreme temperatures and no significant greenhouse effect, which are necessary for liquid water to exist.
Explanation:
Mercury's close proximity to the Sun and its thin atmosphere contribute to conditions that are not conducive to maintaining liquid water on its surface. Due to its small size and weak gravity, Mercury cannot retain a substantial atmosphere, which would be necessary to create a greenhouse effect to keep the heat in. Additionally, the intense solar radiation that Mercury receives results in surface temperatures that can reach up to 800 degrees Fahrenheit (427 degrees Celsius) during the day, which is far too hot for liquid water to exist.
The lack of a significant atmosphere means there is no atmospheric pressure to prevent water from boiling away. Without an atmosphere similar to Earth's, which includes water vapor and carbon dioxide, Mercury is unable to trap heat and maintain steady surface temperatures. Its tenuous atmosphere, composed mainly of trace gases, is incapable of supporting a cycle that would retain liquid water. Therefore, Mercury's environment does not allow for the presence of stable bodies of liquid water on its surface.
Which statement best describes an insulator?
Answer:an insulator does not allow electrons to move through it
Explanation:
Answer:
It has a high resistivity because it opposes the movement of electrons.
Explanation:
APEX
a man lifts a 2.5kg stone vertically with his hand at a constant velocity of 1.2m/s. what is the magnitude of the total force of the man's hand on the stone.
Answer:
Zero
Explanation:
According to Newton's second law of motion, the net force on an object is equal to the product of its mass and its acceleration:
[tex]F=ma[/tex] (1)
where
F is the net force
m is the mass
a is the acceleration
For the stone in this problem, we have:
m = 2.5 kg is its mass
We are also told that the velocity of the stone is constant (1.2 m/s): we know that the acceleration is equal to the rate of change of velocity, therefore, this means that the acceleration (because the change in velocity is zero):
[tex]a=0[/tex]
Therefore, from equation (1), we get that the total net force on the stone is zero:
[tex]F=0[/tex]
Which means that the upward force on the stone balances the downward force of gravity.
Final answer:
To lift a 2.5kg stone at a constant velocity, the man's hand must apply a force equal to the weight of the stone, which is 24.5 N, countering the gravitational pull without causing any acceleration.
Explanation:
The magnitude of the total force of the man's hand on the stone can be determined by Newton's second law of motion which states that the force is equal to mass times acceleration (F=ma). However, since the stone is moving at a constant velocity, the acceleration is zero, and thus the only force exerted by the man would be to counteract the force of gravity on the stone. The force of gravity is calculated as the mass of the stone multiplied by the acceleration due to gravity (g = 9.8 m/s2).
The force of gravity (also known as weight) on the stone can be calculated as follows:
Fg = m × g = 2.5 kg × 9.8 m/s2 = 24.5 N.
Therefore, the magnitude of the total force that the man's hand must apply on the stone to lift it at a constant velocity is 24.5 N, which is exactly the same as the gravitational force acting on the stone.
explain why the sound produced by every vibrating body cannot be heard by us ?
Answer:
The human ear is not sensitive to every frequency of sound, rather, our hearing range is from 20Hz to 20,000Hz. This means sound frequencies outside this range are not audible to the human ear, which is why not every sound produced is heard. This is quite a blessing because if we could hear every vibrating body, then our ears would never stop listening: we won't be able to distinguish 'important sounds' from unimportant ones, rendering our ears effectively useless. Perhaps this is why we have a hearing range in the first place: sounds of our friends and our foes lie in 20Hz-20kHz range.
What happens when light hits a shiny or smooth surface?
A It disappears
B It is refracted
C It is absorbed
D It is reflected.
Answer: D reflected
Explanation:
Answer:
Correct option (D)
Explanation:
The shiny or smooth surface is an interface that acts as a perfectly reflecting surface. When a light ray or a beam of light is allowed to incident onto it, it is reflected to the same medium.
Alice builds an electric motor by positioning an electromagnet between the poles of a permanent magnet. When the electromagnet turns, the current through it switches direction because its connections to the voltage source are reversed. The repeated switching of the electromagnet's poles causes it to spin. This particular motor is used to turn the wheels of a toy car.
Which of the following actions would increase the amount of force applied to the wheels of the toy car?
A.
replacing the magnet with a stronger magnet
B.
increasing the distance between the magnet's poles and the electromagnet
C.
decreasing the number of loops in the electromagnet's coil
D.
decreasing the electric current running through the electromagnet
Answer:
A. replacing the magnet with a stronger magnet
Explanation:
In order to increase the force on the wheels, Alice needs to increase the force acting between the magnet and the electromagnet. There are several ways that she could do this:
replace the magnet with stronger magnet
increase the number of loops in the electromagnet's coil
increase the electric current running through the electromagnet
decrease the distance between the magnet's poles and the electromagnet
Please Answer this....
Class 10 science board cbse 2020
Qn. 29
a) See attachment
b) -180 cm, virtual image
c) Magnification: 10, image is 10 times the size of the object, upright
Explanation:
a)
The ray diagram for this situation is shown in attachment.
In order to find the position of the image, we proceed as follows:
- We draw a ray of light going from the tip of the object towards the lens, parallel to the principal axis - this ray is refracted towards the principal focus on the other side
- We draw another ray of light going from the tip of the object towards the centre of the lens
- We prolong both rays: we see that they don't meet on the right side of the lens. Therefore, we prolong them on the left side, where they meet - this means that the image is virtual, because it cannot be projected on a real screen (it is formed on the same side as the object).
b)
To find the nature and the position of the image, we use the lens equation:
[tex]\frac{1}{f}=\frac{1}{p}+\frac{1}{q}[/tex]
where:
f is the focal length
p is the distance of the object from the lens
q is the distance of the image from the lens
In this problem:
[tex]f=20 cm[/tex] is the focal length
[tex]p=18 cm[/tex] is the object distance
Solving for q, we find the position of the image:
[tex]\frac{1}{q}=\frac{1}{f}-\frac{1}{p}=\frac{1}{20}-\frac{1}{18}=-0.00555 cm^{-1}\\q=\frac{1}{-0.00555}=-180 cm[/tex]
The negative sign indicates that the image is virtual (on the same side of the object).
c)
The magnification is given by:
[tex]M=-\frac{q}{p}[/tex]
where
q is the image distance from the lens
p is the object distance from the lens
Here we have
[tex]q=-180 cm[/tex]
[tex]p=18 cm[/tex]
So the magnification is:
[tex]M=-\frac{-180}{18}=10[/tex]
This means that the image size is a factor 10 times the object size. In fact, we can write
[tex]y'=My[/tex]
where
y' is the image size
y is the object size
Substituting,
[tex]y'=10y[/tex]
So, the image is 10 times the object (in size), and it has the same orientation, upright (because of the positive sign).
A pendulum consisting of a sphere suspended from a light string is oscillating with a small angle with respect to
the vertical. The sphere is then replaced with a new sphere of the same size but greater density and is set into
oscillation with the same angle. How do the period and maximum acceleration of the new pendulum compare to
those of the original?
Period
Acceleration
a. Larger
Smaller
b. Smaller
Larger
C. The same
The same
d. The same
Smaller
Answer:
Explanation:
The time period of a simple pendulum: It is defined as the time taken by the pendulum to finish one full oscillation and is denoted by “T”.
The period of simple pendulum is given as
T=2π√l/g
Increasing the density of the object implies that the mass has increased
Because density is mass/volume
The period is independent on the density of the object, it depends on the length of the string and the acceleration due to gravity. So the period remains the same.
2. Acceleration
The acceleration of a simple pendulum is given as
a=-gSin θ
Therefore the acceleration is independent on the density of the object, it depends on the acceleration due to gravity and the angle of displacement.
Then, the acceleration remains the same.
So the answer is Option C,
Same
Same
Final answer:
Replacing a sphere with another of greater density in a pendulum, without changing the oscillation angle, does not affect the pendulum's period or maximum acceleration. Both remain the same because they are independent of the pendulum bob's mass or density.
Explanation:
The period of a pendulum is given by the formula T = 2π√(l/g), where T is the period, l is the length of the pendulum, and g is the acceleration due to gravity. This formula shows that the period is independent of the mass or density of the pendulum bob. Hence, replacing a sphere in a pendulum with another sphere of greater density but the same size, and oscillating both at the same angle, does not change the period of the pendulum's oscillation. The maximum acceleration of a pendulum occurs at its lowest point and is given by a = g√(sinθ), where θ is the oscillation angle. Since the acceleration depends only on gravity and the angle of oscillation, which remain constant, the maximum acceleration of the pendulum will also remain the same irrespective of the mass or density of the bob.
An instrument that measures atmospheric pressure
Answer:
barometer
Explanation:barometer
A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. A simple barometer consists of a long glass tube (closed at one end, open at the other) filled with mercury and turned upside down into a container of mercury.
brainliestA barometer is the instrument that measures atmospheric pressure. It operates by counterbalancing the weight of a column of mercury against the atmospheric pressure. The level of mercury changes based on the atmospheric pressure.
Explanation:The instrument that measures atmospheric pressure is called a barometer. This device was invented in the 17th century by the Italian scientist Evangelista Torricelli. It works by balancing the weight of a column of mercury against the atmospheric pressure. When the pressure is high, it pushes the mercury higher up the tube, and when it is low, the mercury drops. Digitals variations exist now and are widely used also.
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A baseball (m = 145 g) traveling 32 m/s moves a fielder's glove backward 25 cm when the ball is caught. What was the average force exerted by the ball on the glove?
Answer:
297 N
Explanation:
First, find the acceleration of the ball.
Given:
Δx = 0.25 m
v₀ = 32 m/s
v = 0 m/s
Find: a
v² = v₀² + 2aΔx
(0 m/s)² = (32 m/s)² + 2a (0.25 m)
a = -2048 m/s²
Find the force exerted on the ball by the glove.
F = ma
F = (0.145 kg) (-2048 m/s²)
F = -297 N
The force exerted by the ball on the glove is equal and opposite.
-F = 297 N
Round as needed.
The average force exerted by the ball on the glove when it was caught is 297 N.
The given parameters:
mass of the baseball, m = 145 g = 0.145 kgspeed of the baseball, u = 32 m/sdistance moved, d = 25 cm = 0.25 mThe acceleration of the baseball is calculated as follows
[tex]v^2 = u^2 + 2as\\\\0 = 32^2 + 2(-0.25)a\\\\0 = 1024 - 0.5a\\\\0.5a = 1024\\\\a = 2048 \ m/s^2[/tex]
The average force exerted by the ball on the glove when it was caught is calculated as follows:
[tex]F = ma\\\\F = 0.145 \times 2048\\\\F = 297 \ N[/tex]
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Jimmy has two options for moving a piano up to the second floor of a hotel, which is 10 m above his current position. He can push the piano up 50 m ramp or lift the piano up with a rope wrapped around a pulley. Which option will require him to exert a greater average force? Neglecting friction, which option will require more work?
Answer:
Lifting straight up, even with a rope and pulley, always takes more force than going up a slanted ramp to the same height.
But if you use the ramp, then you have to exert the force over a greater distance (pull more rope to lift to the same height).
Astonishingly, the product of (force) x (distance) is the same number either way. So without friction, the total amount of work required is the SAME whichever way the piano is lifted.
At 15°C air is transmitted
at 340 m/s. Express this speed
in Kilometers per hour.
Answer:
1224km/hr
Explanation:
To convert from m/s to km/hr
1000m = 1km
Divide both sides by 1000
1m = 1/1000 km................. (1)
60×60 seconds = 1 hr
3600s = 1hr
Divide both sides by 3600
1s = 1/3600 .............(2)
Divide (2) by (1)
1m/s = 1/1000 ÷ 1/3600 km/hr
1m/s = 1/1000 × 3600/1 km/hr
1m/s = 3600/1000 km/hr
1m/s = 3.6 km/hr .............(3)
To convert 340m/s to km/hr
Multiply (3) by 340
1× 340m/s = 3.6 × 340 km/hr
340m/s = 1224km/hr
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Answer:
1224 km/hr
Explanation:
Method 1to convert m/s to km/hrrecall that :
1km = 1000m
firstly lets convert m to km
340 m to km
340 / 1000
= 0.34 km
recall that :
1hr = 60 min
1 min = 60 seconds
hence 1 hr = 60*60
1 hr = 3600 seconds
now to convert seconds to hr :1 second / 3600
=1/3600 hours
hence to get the answer you say :
[tex]\frac{0.34}{\frac{1}{3600} }[/tex]
= 1224 Method 2recall : 1km = 1000m
recall: 1hr = 60 min
1 min = 60 seconds
hence 1 hr = 60*60
1 hr = 3600 seconds
now to get this answer you have to divide m by 1000 to get km
and you have to divide seconds by 3600 to get hours
= [tex]\frac{340 / 1000}{1/3600}[/tex]
= 1224Which of the following is a speed, not a velocity?
A. 35 m/s east
B. 0-35 m/s
C. 035 m/s
D. 35 m/s south
Answer:
B. 0-35 m/s
Explanation:
Because speed does not need a direction so it would be 0-35 m/s A and B has a direction, velocity needs a direction and the question ask not velocity. C technically it does not have a speed
Two colours of light which mix to make white light are called
a) primary colours
b) secondry colous
c) complementary colours
d) dye
Complementary colors are pairs of colors that, when mixed together, produce white light. They are located opposite each other on the color wheel.
Explanation:The correct answer is c) complementary colours. Complementary colors are pairs of colors that, when mixed together, produce white light. These colors are located opposite each other on the color wheel. For example, red and cyan, green and magenta, and blue and yellow are complementary color pairs.
Mixing complementary colors can be observed in additive color mixing, which is the process of combining different colors of light. For instance, if you mix red and cyan lights together, you will see white light.
Complementary colors are also used to create contrast and make colors stand out when they are placed next to each other. This concept is often used in design and visual arts.
1. If a model train car with a momentum of 12 kg•m/s collides with a 2 kg model train car that is not moving, what is the total momentum of both cars after the collision?
Answer:
[tex]P_{f} = 12 \ kg.m/s[/tex]
Explanation:
Given data:
Momentum of moving model train, [tex]P_{1} = 12 \ kg.m/s[/tex]
Mass of the stationary model train, [tex]m = 2 \ kg[/tex]
Initial speed of the stationary model train, [tex]v = 0[/tex]
Assume there is no external force is acting on the given train system.
In this case, the total linear momentum of the trains would be conserved.
Let the final linear momentum of the trains be [tex]P_{f}.[/tex]
Thus,
[tex]P_{i} = P_{f}[/tex]
[tex]P_{1} + P_{2} = P_{f}[/tex]
[tex]P_{1} + mv = P_{f}[/tex]
[tex]12 + 2 \times 0 = P_{f}[/tex]
[tex]\Rightarrow \ P_{f} = 12 \ kg.m/s.[/tex]
The total momentum of both cars after the collision is 12 kg•m/s.
Explanation:The momentum of an object is the product of its mass and velocity. In this case, the initial momentum of the moving model train car is 12 kg•m/s while the other car is stationary, so its initial momentum is 0 kg•m/s.
According to the law of conservation of momentum, the total momentum before the collision is equal to the total momentum after the collision. Therefore, the total momentum of both cars after the collision is 12 kg•m/s.
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which four equations can be used to solve for acceleration
The four equations for acceleration are obtained from the three equations of motion and from second law of motion.
Explanation:
Acceleration is defined as the rate of change of velocity with respect to time. So the change in velocity with respect to time can be determined using the three equations of motions.
So from the first equation of motion, v = u + at , we can determine the value of acceleration if time taken, final and initial velocity is known. The equation can be re-written as [tex]a = \frac{v-u}{t}[/tex]
Similarly, from the second equation of motion, s = ut + 1/2 at², we can determine the equation for acceleration as [tex]a = 2*\frac{s-ut}{t^{2} }[/tex]
So this is second equation for acceleration.
Then from the third equation of motion, [tex]v^{2}- u^{2} = 2* a *s[/tex]
the acceleration equation is determined as [tex]a = \frac{v^{2}-u^{2} }{2s}[/tex]
In addition to these three equation, another equation is present to determine the acceleration with respect to force from the Newton's second law of motion. F = Mass × acceleration. From this, acceleration = Force/mass.
So, these are the four equations for acceleration.
6.
Potassium hydroxide (KOH) and hydrochloric acid (HCl) react in a beaker. They form potassium chloride (KCl) and water (H2O). What type of reaction is this? (2 points)
Synthesis reaction
Double replacement reaction
Single replacement reaction
Decomposition reaction
Answer:it is a double replacement reaction
Explanation:
It's a double replacement reaction
A youngster having a mass of 50.0 kg steps off a 1.00 m high platform. If she keeps her legs fairly rigid and comes to rest in 10.0 ms, what is her momentum just as she hits the floor? What average force acts on her during the deceleration?
The youngster's momentum just before hitting the floor is -500 kg*m/s, and the average force acting on her during deceleration is 25,000 N.
Explanation:To calculate momentum before hitting the floor, we use the formula: momentum = mass × velocity. Given the mass (m) as 50.0 kg and the height (h) as 1.00 m, we can find the initial velocity (v) using the equation for gravitational potential energy (PE = mgh) and converting it into kinetic energy (KE = 1/2mv^2). Solving for velocity, we get v = √(2gh) = √(2 × 9.81 m/s^2 × 1.00 m) ≈ 4.43 m/s.
Momentum = mass × velocity = 50.0 kg × 4.43 m/s = 221.5 kg*m/s. As she comes to rest, the change in momentum is Δp = final momentum - initial momentum = 0 - 221.5 kg*m/s = -221.5 kg*m/s. However, as the motion direction changes, the momentum also changes direction, so we take -221.5 kg*m/s as the momentum just before hitting the floor.
The average force during deceleration can be found using the impulse-momentum theorem, which states that impulse (change in momentum) is equal to force × time. Impulse = Δp = force × time. Rearranging the formula to solve for force, we get force = Δp / time. Substituting the values, force = -221.5 kg*m/s / (10.0 ms) = -22,150 N.
However, force is a vector quantity, and its direction opposes the motion, so the magnitude of the force is 22,150 N. As the force acts over 10.0 ms, the average force is 22,150 N / 10.0 ms = 25,000 N. Thus, the average force exerted on the youngster during deceleration is 25,000 N, with the negative sign indicating it opposes the motion.