Question: A pile driver drives a post into the ground. The mass of the pile driver is 2 500 kg and it is dropped through a height of 8.0 m on each stroke. If the resisting force of the ground is 4.0 × 10⁶ N, how far is the post driven in on each stroke?
Answer: 4.9 cm
Question: A girl and her bicycle have a total mass of 40.0 kg. At the top of the hill her speed is 5.0 m/s, and her speed doubles as she rides down the hill. The hill is 10.0 m high and 100 m long. How much kinetic energy and potential energy is lost to friction?
Answer: 2 420 J
Question: I drop a 60-g golf ball from 2.0 m high. It rebounds to 1.5 m. How much energy is lost?
Answer: 0.29 J
Question: A horizontal force is applied to a 4.0 kg box. The box starts from rest moves a horizontal distance of 8.0 meters and obtains a velocity of 6.0 m/s. The system is frictionless. What is the horizontal force?
Answer: 9 N
Question: A 5.0 kg box slides up a 10 m long frictionless incline at an angle of 20 degrees with the horizontal pushed by a 40 Newton force parallel to the incline. What is the change in kinetic energy?
Answer: 232 J
Question: A 20 kg box slides down a 12.0 m long frictionless incline at an angle of 30 degrees with the horizontal. A force of 50 N is applied to the box to try to pull it up the incline. The applied force makes an angle of 10 degrees to the incline and above the incline. What is the increase in the kinetic energy of the box?
Answer: 585 J
Question: The graph shows the force on an object as it moves a distance x. What is the work done by the force when the object moves from 0.0 m to 10.0 m?
Answer: 64 J
Question: A spring-powered dart gun is un-stretched and has a spring constant 12.0 N/m. The spring is compressed by 8.0 cm and a 5.0 gram projectile is placed in the gun. What is the velocity of the projectile when it is shot from the gun?
Answer: 3.92 m/s
Question: A 60-kg woman runs up a flight of stairs having a rise of 4.0 m in a time of 4.2 s. What average power did she supply?
Answer: 560 W
Question: Water flows over a section of Niagara Falls at a rate of 1.20 × 10⁶ kg/s and falls 50.0 m. What is the power dissipated by the waterfall?
Answer: 588 MW
Question: A 1 000-kg sports car accelerates from zero to 25 m/s in 7.5 s. What is the average power delivered by the automobile engine?
Answer: 41.7 kW
Question: A force of 5.0 N is applied to a 20-kg mass on a horizontal frictionless surface. As the speed of the mass increases at a constant acceleration, what happens to the power delivered to it by the force? It remains the same, increases, or decreases?
Answer: Increases
Question: A 100-W light bulb is left on for 10.0 hours. Over this period of time, how much energy was used by the bulb?
Answer: 3 600 000 J
Question: A 30 kg mass falls from a height of 4.0 m. What is the momentum of the mass just before it hits the ground?
Answer: 265.6 kg m/s