A 567-kg trailer is hitched to a truck. Find the work done by the truck on the trailer in each of the following cases. Assume rolling friction is negligible. (a) The trailer is pulled at constant speed along a level road for 1.54 km. kJ (b) The trailer is accelerated from rest to a speed of 88.5 km/h. kJ (c) The trailer is pulled at constant speed along a road inclined at 12.8°for 1.54 km. kJ

A 7.80-g bullet moving at 570 m/s penetrates a tree trunk to a depth of 4.40 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 enters the tree and the moment it stops moving.

A hummingbird hovers by exerting a downward force on the air equal, on average, to its weight. By Newton's third law, the air exerts an upward force of the same magnitude on the bird's wings. Find the average mechanical power (in W) delivered by a 3.60 g hummingbird while hovering if its wings beat 75.0 times per second through a stroke 3.98 cm long. HINT To find the average power per stroke, calculate the work done each stroke and divide by the time per stroke. Click the hint button again to remove this hint.

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When an automobile moves with constant speed down a highway, most of the power developed by the engine is used to compensate for the mechanical energy loss due to frictional forces exerted on the car by the air and the road. If the power developed by the engine is 195 hp, estimate the total friction force acting on the car when it is moving at a speed of 30 m/s. One horsepower equals 746 W.

A crate is given a push across a horizontal surface. The crate has a mass m, the push gives it an initial speed of 3.60 m/s, and the coefficient of kinetic friction between the crate and the surface is 0.130. (a) Use energy considerations to find the distance (in m) the crate moves before it stops.   ____m   (b) What If? Determine the stopping distance (in m) for the crate if its initial speed is doubled to 7.20m/s.   ____m

A 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 enters the tree and the moment it stops moving.

You throw a tennis ball (mass 0.0570 kg) vertically upward. It leaves your hand moving at 15.0 m/s. Air resistance cannot be neglected, and the ball reaches a maximum height of 8.00 m. (a) By how much does the total mechanical energy decrease from when the ball leaves your hand to when it reaches its maximum height? (b) What is the magnitude of the average force of air resistance?

A 7.80-g bullet moving at 640 m/s penetrates a tree trunk to a depth of 6.10 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 enters the tree and the moment it stops moving.

A 35 kg sled slides along a horizontal surface on which the coefficient of kinetic friction is 0.25. Its velocity at point A is 10.0 m/s, and its velocity at point B is 2.0 m/s. You must use Work/Energy methods (not Kinematics). (a) What is the frictional force acting on the sled? (b) How much work is done on the sled by friction over the displacement ∆x = xB − xA? (c) What is the distance the sled travels between A and B?