Physics Work,Power & Energy Level: Misc Level
3 -A ball of mass 2 Kg is dropped from a height of 10 m. The speed of the ball is measured as 12.5 m/s just before it hits the ground. What was the work done against air friction during this fall?
Physics Work,Power & Energy Level: Misc Level
A 70 kg athlete climbs a rope in the gymnasium at a constant speed of 0.700 m/s.what is the average power (in watts ) developed in the process?If the athlete climbs 5 meters, what is the amount of work done? How much time does climb the 5 meters?
Physics Work,Power & Energy Level: Misc Level
A 20.0 gram ( better make it .0200 kg) bullet is fired horizontally at a slab of wood that is 3.00 cm (better make it 0.0300 m) thick. The bullet hed an initial velocity of 300 m/s. The bullet exits the other side of the wood with a velocity of 280 m/s. What is the change in kinetic energy of the bullet in this process? How much work is done on the bullet by the wood?what is the average acceleration of the bullet while traversing the slab of wood? what is the average force of thewood on the bullet?
Physics Work,Power & Energy Level: Misc Level
A 70 kg cart is pushed for 50 m with a constant velocity upon a 45% frictionless incline. Find the work done on the cart. ( Assume g = 10 m/s2)
Physics Work,Power & Energy Level: Misc Level
A 0.4 kg ball is thrown vertically upward with a speed of 30 m/s. The ball reaches a height of 40 m. Assuming g =10 m/s 2, the energy dissipated due to air friction is:
Physics Work,Power & Energy Level: Misc Level
How fast must a 10.5 g bullet be traveling when it strikes a ballistic pendulum that consists of a block of wood of mass 3.0 kg that is suspended by a cord? The bullet gets embedded in the block. The block rises by 0.22 m after the impact.
Physics Work,Power & Energy Level: Misc Level
Approximately what running speed would an 80 kg polevaulter have to acquire to clear a bar 5.0 m off the ground? Assume that the pole- vaulter,s center of gravity is initially 1.0 m off the ground and that the vaulter clears the bar if his center of gravity just reaches the height of the bar.
Physics Work,Power & Energy Level: Misc Level
(a) A spring is hung from a ceiling and a 500 g mass is hung from it. This increases the length of the spring by 20.0 cm. what is the force constant k for the spring?
(b) If the same spring is then moved from the ceiling to a wail and stretched horizontally so that the 500 g mass is displaced 40.0 cm from its equilibrium position, what is the stored potential energy in the spring?
Physics Work,Power & Energy Level: Misc Level
A workman pushes a 200 kg crate up a frictionless meetal ramp of length 4.00 m into the back of a truck (See figure below).
(a) If the angle made by the ramp with the ground is 25.0 degrees and the workman pushes the block at a very slow, constant speed, how much work does he do?
(b) what is the increased gravitational potential energy of the crate
Physics Work,Power & Energy Level: Misc Level
A 100 kg man pulls his 30.0 kg daughter on a sled with a rope that makes an angle of 40.0 degrees with respect to the ground.
(a) If the man exerts a force of 50.0 N and the sled moves 100 m, how much work does he do?
(b) If the man pulls horizontaliy on the sled, what force would he have to exert to do the same amount of work?
Physics Work,Power & Energy Level: Misc Level
Lisa runs up 4 flights of stairs in 22 s. She weighs 510 N. If each flight rises 310 cm:
(a) What is her change in potential?
(b) What average power ( watts ) was required during the 22 s?
(c) What minimum horsepower motor would be required to do this?
Physics Work,Power & Energy Level: Misc Level
As plant engineer, Donna purchases an electrical motor which has an 1500 hp. If it requires 1.20 MW of electricity, what is the efficiency motor?
Physics Work,Power & Energy Level: Misc Level
A spring is characterized by a spring constant of 60 N/m. How much energy does it store, when stretched by 1.0 cm?
Physics Work,Power & Energy Level: Misc Level
A driver, traveling at 22 m/s,slows down her 1500 kg car to stop for a red light. what work is done by the friction force against the wheels?
Physics Work,Power & Energy Level: Misc Level
A man with a mass of 55 kg skis down a frictionless hill that is 2.1 m high. At the bottom of the hill the terrain levels out. As the man reaches the horizontal section, he grabs a 20 kg backpack and skis off a 2.0 m high ledge. At what horizontal distance from the edge of the ledge the man land?
