Work and Energy Review Problems (Answers are at the bottom of this document)

1. From the given list, select a possible pair for the value of coefficient of static and kinetic frictions μs and μk (There may be more than one choice)
a. (2.61, 2.00) b. (2.00, 2.61) c. (0.261, 0.150) d. (0.150, 0.261)

2. A runner has a kinetic energy of 750 J. What will be his/her kinetic energy if
(a) his/her mass is doubled.
(b) his/her speed is doubled.

3. Three objects were thrown from top of a building. First one was thrown with 20 m/s horizontally. The second one was thrown vertically upward with an initial speed of 20 m/s. The third object was thrown at an angle 30o to the horizontal. When the objects reach the ground, which object will have the highest speed?

4. A 2.5 x 103 kg car starts from rest at the top of a 20 m rough slope inclined at 30o with the horizontal. If the average frictional force experienced by the car is 3.2 x 103 N, find the speed of the car at the bottom of the slope.

5. The electric motor of a toy car accelerates the car from rest to 0.5 m/s in 0.030 s. If the mass of the toy car is 3.0 kg, find the average power delivered to the car during its acceleration.

1. Coefficient of friction can only assume values between 0 and one. i.e.
0 ≤ μs ≤ 1 0 ≤ μk ≤ 1. Further, coefficient of static friction is larger than coefficient of kinetic friction. i.e. μs > μk
So the only possible choice is choice C.

2. Formula for kinetic energy is: K = ½ m v2
Note that K is proportional to m. Hence if we double the mass, kinetic energy also should double. So the new kinetic energy must be 2 x 750 = 1500 J
Note that K is proportional to v2 ...

Solution Summary

This document contains five problem on the topic of 'Work and Energy'. First three problems test the conceptual understanding of this topic while the other two tests the problem solving skills. I have provided detailed step-by-step solution to all the problems. I also have included colorful clear labeled diagrams to further clarify the problems at hand. I created these problem set for my college level students for review and I believe these will benefit you as well.

1) an object initially at rest reaches a velocity of 30m/s in 6 seconds, how much work is done during this time interval?
2) a roller coaster car with a mass of 1000kg starts at ground level and reaches a maximum height of 128m. what is the change in potential energy for the car? I f all the potential energy is turned into ki

Pushing a Cat. Your cat "Ms." (mass 7.00 kg) is trying to make it to the top of a frictionless ramp 2.00 m long and inclined upward at 30.0 degree above the horizontal. Since the poor cat can't get any traction on the ramp, you push her up the entire length of the ramp by exerting a constant 100-N force parallel to the ramp.

The only force acting on a 2.4 kg body as it moves along the x axis varies as shown in Fig. 7-33 (attached). The velocity of the body at x = 0 is 4.0 m/s.
(a) What is the kinetic energy of the body at x = 3.0 m?
(b) At what value of x will the body have a kinetic energy of 8.0 J?
(c) What is the maximum kinetic energy attai

I'm having a diffucult time understanding free energy vs activation energy
are they the same?
I know free energy is the portion of a system's energy that is available for work
but what is this compared to the activiation energy?

Which of the following statements are true about the hydrogen atom's energy levels? Support your answers with explanation.
1. 13.6 eV is enough energy to ionize Hydrogen, which means exciting an electron from n = 1 up to zero energy.
2. The wavelength of a photon emitted from the n=3 to n=2 transition is longer than that emi

Radiation of a certain wavelength causes electrons with a maximum kinetic energy of 0.62 eV to be ejected from a metal whose work function is 2.65 eV. What will be the maximum kinetic energy (in eV) with which this same radiation ejects electrons from another metal whose work function is 2.01 eV? Units are in eV.

When an average force F is exerted over a certain distance on a shopping cart of mass m, its kinetic energy
increases by 12 mv2.
(a) Use the work-energy theorem to show that the distance over which the force acts is mv2/2F.
Am I on the right track? UGH so very frustrated!
Kinetic energy = 1/2 mass x speed2
KE = 1/

1. During a rockslide, a 520 kg rock slides from rest down a hillside that is 500m long and 300m high. The coefficient of kinetic friction between the rock and the hill surface is 0.25
(a) If the gravitational potential energy U of the rock-Earth system is zero at the bottom of the hill, what is the value of U just before the

Question: A 16-kg sled is being pulled along the horizontal snow-covered ground by a force of 24 N. Starting from rest, the sled attains a speed of 2.0 m/s in 8.0 m. Find the coefficient of kinetic friction between the runners of the sled and the snow.