Final answer:
Using Newton's law of cooling, we can calculate that the beer will be approximately 60.4ºF if left out for 20 minutes.
Explanation:
To calculate the final temperature of the beer after being left out for 20 minutes, we can use Newton's law of cooling. This law states that the rate of heat loss of an object is proportional to the temperature difference between the object and its surroundings. In this case, the initial temperature of the beer is 40ºF and the room temperature is 70ºF. Let's determine the constant of proportionality, k, first:
k = (T2 - T1) / t = (70 - 40) / 3 = 10
Now we can use the formula to find the final temperature, T3, after 20 minutes:
[tex]T3 - 70 = (40 - 70)e^(-10(20/3))[/tex]
[tex]T3 - 70 = -30e^(-20/3)[/tex]
[tex]T3 = 70 - 30e^(-20/3)[/tex]
Using a calculator, we can find that T3 is approximately 60.4ºF.
When exiting the highway, a 1100-kg car is traveling at 22 m/s. The car's kinetic energy decreases by 1.4×105J The exit's speed limit is 35 mi/h. Did the driver reduce its speed enough?
Answer: The final velocity is 33.78 mi/h, so the driver did reduced his speed enough.
Explanation: The kinetic energy of an object can be calculated as:
K = (1/2)m*v^2
We know that the mass of the car is m=1100kg
and the initial velocity is 22m/s
The initial kinetic energy is:
K = (1/2)*1100*(22)^2 = 266,200 joules.
Now, if the kinetic energy decreases by 1.4x10^5 J, the new kinetic energy is:
K = 266,200j - 140,000j = 126,200j
So we now can find the new velocity in m/s.
126,200 = (1/2)*1100*v^2
126,200*2/1100 = v^2
229.45 = v^2
v = (229.45)^(1/2) = 15.1 m/s
We know that the limit is 35 mi/h, so we need to transform our result into miles per hour.
We know that in one hour, there are 3600 seconds, so the velocity per hour is:
15.1*3600 m/h = 54,360 m/h
and we know that one mile is 1609.34 meters, so we need to divide by 1609.34.
v = (54,360/1609.34) mi/h = 33.78 mi/h
this is less than the speed limit, so the driver reduced his speed enough.
After losing kinetic energy, the car's final velocity was approximately 18.99 m/s, exceeding the exit's speed limit of 15.64 m/s, hence the driver did not reduce their speed adequately.
Explanation:To determine whether the driver reduced their speed enough when exiting the highway, we must calculate the car's speed after its kinetic energy decreases by 1.4×105J. The initial kinetic energy (KE) of the 1100-kg car traveling at 22 m/s can be calculated using the equation KE = ½ mv². Plugging in the values, we can find the initial kinetic energy:
KEinitial = ½ (1100 kg)(22 m/s)² = 5.28×105J
After losing 1.4×105J of energy, the remaining kinetic energy will be:
KEfinal = KEinitial - 1.4×105J = (5.28 - 1.4)×105J = 3.88×105J
We can solve for the final velocity (vfinal) using the remaining kinetic energy:
½ (1100 kg)vfinal² = 3.88×105J
vfinal = √((2×3.88×105J) / 1100 kg)
vfinal ≈ 18.99 m/s
To compare to the speed limit, we convert 35 mi/h to meters per second:
35 mi/h × 0.44704 (conversion factor) = 15.64 m/s
Since the final velocity of the car is 18.99 m/s, which is greater than the exit's speed limit of 15.64 m/s, the driver did not reduce their speed enough.
If a force of 10 n is applied to an object with a mass of 1kg the object will accelerate at