1. A car drives 5.0 km north, then 7.3 km east, then 6.7 km northeast, all at a constant velocity. If the car had to perform 2.6 × 106 J of work during this trip, what was the magnitude of the average frictional force on the car?

1. A car drives 5.0 km north, then 7.3 km east, then 6.7 km northeast, all at a constant velocity. If the car had to perform 2.6 × 106 J of work during this trip, what was the magnitude of the average frictional force on the car?
2. A spring with a spring constant of 10 N/m is stretched from equilibrium to 2.9 m. How much work is done in the process?
3. 300 J of work are required to fully drive a stake into the ground. If the average resistive force on the stake by the ground is 355 N, how long is the stake?
4. Three cars (car L, car M, and car N) are moving with the same velocity, and slam on the brakes. The most massive car is car L, and the least massive is car N. Assuming all three cars have identical tires, for which car is the amount of work done by friction in stopping it the highest?
5. Sue and Betti both ski straight down a hill, both starting from rest. Sue weighs more than Betti. Neglecting friction and wind resistance, which skier will be moving the fastest at the bottom of the hill?
6. 188 J of work are needed to stretch a spring from 1.4 m to 2.9 m from equilibrium. What is the value of the spring constant?
7. A traveler pulls on a suitcase strap at an angle 36° above the horizontal. If 325 J of work are done by the strap while moving the suitcase a horizontal distance of 15 m, what is the tension in the strap?
8. How much work must be done by frictional forces in slowing a 1000.0 kg car from 27.8 m/s to rest?
9. A 31 g bullet pierces a sand bag 24 cm thick. If the initial bullet velocity was 31 m/s and it emerged from the sandbag with 13 m/s, what is the magnitude of the friction force (assuming it to be constant) the bullet experienced while it traveled through the bag?
10. 4.00 × 105 J of work are done on a 1033 kg car while it accelerates from 10.0 m/s to some final velocity. Find this final velocity.
11. A child pulls on a wagon with a force of 75 N. If the wagon moves a total of 42 m in 3.2 min, what is the average power generated by the child, in watts?
12. A spring-loaded dart gun is used to shoot a dart straight up into the air, and the dart reaches a maximum height of 24 meters. The same dart is shot up a second time from the same gun, but this time the spring is compressed only half as far (compared to the first shot). How far up does the dart go this time (neglect friction and assume the spring obeys Hooke’s law)?
13. Three cars with identical engines and tires start from rest, and accelerate at their maximum rate. Car X is the most massive, and car Z is the least massive. Which car needs to travel the furthest distance before reaching a speed of 60 mi/h?
14. A 5.7 m massless rod is loosely pinned to a frictionless pivot at 0. A 4.0 kg ball is attached to the other end of the rod. The ball is held at A, where the rod makes a 30° angle above the horizontal, and is released. The ball-rod assembly then swings freely in a vertical circle between A and B. In the figure, the ball passes through C, where the rod makes an angle of 30° below the horizontal. The speed of the ball as it passes through C is closest to:
15. A spiral spring is compressed so as to add U units of potential energy to it.
When this spring is instead stretched two-thirds of the distance it was compressed, its remaining potential energy in the same units will be.