Answer:
JJ. Thomson- electrons mixed in a positive sphere
Ernest Rutherford- central nucleus
Democritus and Dalton- indivisible sphere
Explanation:
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Ernest Rutherford discovers the Concept of nucleus. J.J Thompson contributes to the Discovery of electrons. Dalton gives the concept of the Indivisibility of atoms.
A. Ernest Rutherford: Contribution - Concept of the nucleus. Rutherford's famous Gold Foil Experiment led to the discovery that most of the atom's mass and positive charge are concentrated in a small, dense nucleus at the center of the atom.
B. J.J. Thompson: Contribution - Discovery of electrons. J.J. Thompson discovered electrons using cathode ray tubes and proposed the "Plum Pudding Model," which suggested that atoms contained negatively charged electrons embedded in a positively charged material.
C. Dalton: Contribution - Indivisibility of atoms. Dalton's Atomic Theory proposed that matter is made up of indivisible and indestructible particles called atoms, which combine to form compounds in fixed ratios.
Therefore, Ernest Rutherford discovers the Concept of the nucleus. J.J Thompson contributes to the Discovery of electrons. Dalton gives the concept of the Indivisibility of atoms.
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The complete question is:
Match column A (name of the Scientists) with column B (their contributions towards the understanding of the atomic structure).
Column A Column B
A. Ernest Rutherford 1. Indivisibility of atoms
B. J.J Thompson 2. Concept of nucleus
C. Dalton 3. Discovery of electrons
What are the similarities and differences between chemical and physical properties?
Answer:
Physical properties are different from chemical properties of a substance. The main difference between physical and chemical properties is that physical properties can be observed without changing the chemical composition of a substance whereas chemical properties can be observed by changing the chemical composition of a substance.
Explanation:
The differences are:
1. Physical change is easily reversible while chemical change is not easily reversible
2. Physical change forms no new substance. while chemical change forms new substance
3. In Physical change there is no change in the mass of a substance involved while In chemical change, there is a change in the mass of the substance involved.
4. Physical change does not involve great heat. while chemical change involves considerable amount of heat.
The Similarities are :
1. They can be both reversible.
2. Heat is involved
3. They both involve reasonable amount of substance or matter.
Physical properties exhibit physical changes such as:
boiling and melting point of a substance, density, hardness, malleability, crystalline form and some properties that can be detected by our sense organ, such as taste, color and odor.
While chemical properties occur when matter or substance undergoes a change to form another new substance. For example : rusting of iron and burning of wood.
The differences are:
1. Physical change is easily reversible while chemical change is not easily reversible
2. Physical change forms no new substance. while chemical change forms new substance
3. In Physical change there is no change in the mass of a substance involved while In chemical change, there is a change in the mass of the substance involved.
4. Physical change does not involve great heat. while chemical change involves considerable amount of heat.
The Similarities are :
1. They can be both reversible.
2. Heat is involved
3. They both involve reasonable amount of substance or matter.
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Organisms have very few parts that are not useful to the organism. This is because
Answer:
Those parts have become vestigial
Explanation:
Organisms have few parts that are not useful to them because those parts in them have become vestigial.
When an organism has a part is no more using, it relates to the evolutionary history of such organism.
These parts are called vestigial body parts. They are not needed for the survival of an organism again and they can do without them. At a certain point in time, those parts might be very vital to the sustenance of such organism. With time, those parts becomes useless and redundant.Answer:
Those parts have become vestigial
Explanation:
Organisms have a few parts that are not useful to them because those parts in them have become vestigial.
When an organism has a part that is no more used, it relates to the evolutionary history of such organism.
These parts are called vestigial body parts.
They are not needed for the survival of an organism again and they can do without them.
At a certain point in time, those parts might be very vital to the sustenance of such organisms.
With time, those parts become useless and redundant.
How much force is required (in Newton’s) to accelerate a 4-kg skateboard, along with its 46-kg rider, at 3m/s2?
Answer:150N
Explanation:
Total mass=mass of skate board + mass of rider
Total mass(m)=46kg + 4kg
Total mass(m)=50kg
Acceleration(a)=3m/s^2
Force(f)=mass x acceleration
Force=50 x 3
Force=150N
To accelerate the skateboard and rider at 3 m/s², a force of 150 N is required.
The force required to accelerate a 4-kg skateboard and its 46-kg rider at 3 m/s² can be calculated using Newton's second law, which states that Force = mass x acceleration.
Applying the formula, the total mass is 4 kg + 46 kg = 50 kg.
Therefore, the force required is 50 kg x 3 m/s² = 150 N.
Kent throws a tennis ball that has a mass of 3.0 kg straight up in the air at 25 m/s. What height does it reach if the kinetic energy of the ball is 100% transferred into potential energy at the top of the throw
Explanation:
1/2mv^2 = mgh
1/2×3×25^2 = 3×9.8×h
937.5 =29.4h
29.4h/29.4 = 937.5/29.4
h=31.89 m
Which phase of matter consists of particles that vibrate only?
Answer: Solids
Explanation: Solids have very little movement and the particles have barely enough movement to vibrate. We can't see it but the particles are indeed vibrating. Solids have the least amount of kinetic energy which is moving energy.
Many people are familiar with the fact that a rifle recoils when fired. This recoil is the result of
action-reaction force pairs. A gunpowder explosion creates hot gases which expand outward
allowing the rifle to push forward on the bullet. Consistent with Newton's third law of motion,
the bullet pushes backwards upon the rifle. The acceleration of the recoiling rifle is ..
A. greater than the acceleration of the bullet.
B. smaller than the acceleration of the bullet.
Or
C.the same size as the acceleration of the bullet.
Explain your answer.
Answer: b
The force on the rifle equals the force on the bullet. Yet, acceleration depends on both force and mass. The bullet has a greater acceleration due to the fact that it has a smaller mass. Remember: acceleration and mass are inversely proportional
An Inter City Express train traveling at 250 km/h is
braked to a stop in a distance of 4820 m. If the mass of the
train is 8.63 X 105 kg, what is the average braking force?
Answer:
F = 431671.31 [N]
Explanation:
This problem can be solved using the work and energy theorem, which tells us that the initial mechanical energy (potential energy + kinetic energy) plus the sum of the work from the initial position to the end will be equal to the final mechanical energy.
[tex]E_{M1}+W_{1-2}=E_{M2}\\0.5*m*v_{1}^{2}+W_{1-2}=0.5*m*v_{2}^{2}[/tex]
As the train stops at the end, the speed at Point 2 is equal to zero,so we can determine the work, we first convert the speed from [km/h] to meters per second.
[tex]250[\frac{km}{h}]*1[\frac{h}{3600s} ]*1000[\frac{m}{1km} ]\\= 69.44[\frac{m}{s} ][/tex]
[tex]0.5*(8.63*10^{5})*(69.44)^{2}+W_{1-2}= 0.5*(8.63*10^{5})*(0)^{2}\\W_{1-2}=-2080.66*10^6[J][/tex]
The negative sign means that the work is done in the opposite direction to the movement.
Knowing the work we can calculate the force, since an initial input data is the distance
W = F * d
F = W / d
F = (2080.66*10^6) / 4820
F = 431671.31 [N]
How much kinetic energy does a 4.50kg block with a speed of 5.00m/s have?
O
11.23
28.13
5.62)
56.23
Answer:
56.25J
Explanation:
Kinetic energy = 1/2 mv^2
Where m = mass
v = velocity
Given m = 4.50kg
v = 5.00m/s
Kinetic energy = 1/2 x 4.50 x (5.00)^2
= 1/2 x 4.50 x (5.00 x 5.00)
= 1/2 x 4.50 x 25
Multiply through
= 112.5/2
= 56.25J
2 resistors of resistance 1000 ohm and 2000 ohm are joined in series with a 100V supply. A voltmeter of internal resistance 4000 ohm is connected to measure the potential difference across 1000 ohm resistor. Calculate the reading shown by the voltmeter.
The potential difference across a resistor measured using a voltmeter takes into account the internal resistance of the voltmeter, altering the circuit dynamics. Calculations involve finding the equivalent resistance of the voltmeter-resistor parallel combination and applying Ohm's law accordingly.
Explanation:When measuring the potential difference across a resistor in a series circuit using a voltmeter, it is essential to consider the internal resistance of the voltmeter itself, as it is placed in parallel with the resistor being measured. In this case, with resistors of 1000 ohm and 2000 ohm connected in series to a 100V supply and a voltmeter of 4000 ohm internal resistance connected across the 1000 ohm resistor, the circuit's behavior is modified. First, calculate the total series resistance, which is 3000 ohms. This gives a total current (I) of 100V/3000 ohms = 0.0333 A. The voltage across the 1000 ohm resistor without the voltmeter would be V = IR = 0.0333A × 1000 ohm = 33.3V.
However, the presence of the voltmeter alters this calculation by creating a parallel circuit with the 1000 ohm resistor and the voltmeter's 4000 ohm resistance. The equivalent resistance of this parallel circuit can be calculated with 1/Req = 1/R1 + 1/R2, leading to an equivalent resistance of 800 ohms. Applying Ohm's law again for the modified circuit gives a slightly different current, and subsequently, the potential difference can be calculated.
If the average mass of an adult is 86kg. Determine the mass and weight of an 86kg man in the moon where gravitational field is one-sixth that of the earth.
Answer:
See the explanation below, and the different answers
Explanation:
It is important to clarify that the mass is always preserved, that is, it does not vary regardless of the location of the person, whether the moon, Saturn, Mars. The value that changes is the weight, due to the gravity of each planet.
On Earth
m = 86[kg]
w = m * g
where:
g = gravity acceleration = 9.81[m/s^2]
w = weight = [N]
w = 86 * 9.81
w = 843.66 [N]
On the Moon
m = 86[kg]
w = m * g
where:
g = gravity acceleration * (1/6) = 9.81 * (1/6) = 1.635 [m/s^2]
w = weight = [N]
w = 86 * 1.635
w = 140.61 [N]
The mass of the man would still be 86kg, but his weight on the moon would be approximately 14.33kg.
Explanation:To determine the mass and weight of an 86kg man on the moon, where the gravitational field is one-sixth that of Earth's, we can use the equation:
Weight = mass x gravitational field
Since the mass of the man is 86kg, the weight on the moon would be:
Weight = 86kg x (1/6) = 14.33kg
Therefore, the mass of the man would still be 86kg, but his weight on the moon would be approximately 14.33kg.
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