7.80-g bullet moving at 560 m/s penetrates a tree trunk to a depth of 4.80 cm. (a) Use work and energy considerations to find the average frictional force that stops the bullet. (b) Assuming the frictional force is constant, determine how much time elapses between the moment the bullet

A 7.80 g bullet is initially moving at 660 m/s just before it penetrates a block of wood to a depth of 4.40 cm.   (a) What is the magnitude of the average frictional force (in N) that is exerted on the bullet while it is moving through the block of wood? Use work and energy considerations to obtain your answer. _______________N   (b) Assuming the frictional force is constant, how much time (in s) elapses between the moment the bullet enters the block of wood and the moment it stops moving? _______________s

An airplane pilot fell to the ground after jumping from an aircraft without his parachute opening. He lands in a snowbank, creating a crater 2.1 m deep, but survived with only minor injuries.  Assuming the pilot’s mass was 68 kg and his terminal velocity was 35 m/s (the velocity at the point he stopped accelerating on his way down), what is: a) the average force exerted on him by the snow in bringing him to rest?  b) the work done by the snow?

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A 7.80-g bullet moving at 690 m/s penetrates a tree trunk to a depth of 5.10 cm. (a) Use work and energy considerations to find the average frictional force that stops the bullet.N(b) Assuming the frictional force is constant, determine how much time elapses between the moment the bullet enters the tree and the moment it stops moving.s

A 7.80-g bullet moving at 520 m/s penetrates a tree trunk to a depth of 6.30 cm. Answer parts a-b.

A 7.80-g bullet moving at 600 m/s penetrates a tree trunk to a depth of 4.80 cm. (a) Use work and energy considerations to find the average frictional force that stops the bullet.N(b) Assuming the frictional force is constant, determine how much time elapses between the moment the bullet enters the tree and the moment it stops moving.

A 7.80 g bullet is initially moving at 650 m/s just before it penetrates a tree trunk to a depth of 4.70 cm. (a) What is the magnitude of the average frictional force (in N) that is exerted on the bullet while it is moving through the tree trunk? Use work and energy considerations to obtain your answer.   b)  Assuming the frictional force is constant, how much time (in s) elapses between the moment the bullet enters the tree trunk and the moment it stops moving?

When jogging at 13 km/h on a level surface, a 70-kg man uses energy at a rate of approximately 850 W. Using the facts that the “human engine” is approximately 25% efficient, determine the rate at which this man uses energy when jogging up a 5.0° slope at this same speed. Assume that the frictional retarding force is the same in both cases.

A 2.5 kg rock is released from rest at the surface of a pond 1.8m deep. As the rock falls, a constant upward force of 4.3N is exerted on it by water resistance. Let y=0 be at the bottom of the pond.A) Calculate the gravitational potential energy of the system, U, when the depth of the rock below the water's surface is 0.50 m.B) Calculate the kinetic energy of the rock, K, when the depth of the rock below the water's surface is 0.50m.C) Calculate the total mechanical energy of the system, E, when the depth of the rock below the water's surface is 0.50m.