Exam 7: Work and Kinetic Energy

Three cars (car L,car M,and car N)are moving with the same speed and slam on their brakes.The most massive car is car L,and the least massive is car N.If the tires of all three cars have identical coefficients of kinetic friction with the road surface,for which car is the amount of work done by friction in stopping it the greatest?

You throw a baseball straight up.Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.

A person carries a 25.0-N rock through the path shown in the figure,starting at point A and ending at point B.The total time from A to B is 1.50 min.How much work did gravity do on the rock between A and B?

What is the minimum energy needed to change the speed of a 1600-kg sport utility vehicle from 15.0 m/s to 40.0 m/s?

A 30-N box is pulled upward 6.0 m along the surface of a ramp that rises at 37° above the horizontal.How much work does gravity do on the box during this process?

A driver,traveling at 22 m/s,slows down her 2000 kg truck to stop for a red light.What work is done on the truck by the friction force of the road?

An ideal spring has a spring constant (force constant)of 2500 N/m.is stretched 4.0 cm.How much work is required to stretch the spring by 4.0 cm?

Two men,Joel and Jerry,push against a car that has stalled,trying unsuccessfully to get it moving.Jerry stops after 10 min,while Joel is able to push for 5.0 min longer.Compare the work they do on the car.

A crane lifts a 425 kg steel beam vertically upward a distance of How much work does the crane do on the beam if the beam accelerates upward at 1.8 m/s²? Neglect frictional forces.

When you drop a pebble from height H,it reaches the ground with kinetic energy K if there is no air resistance.From what height should you drop it so it will reach the ground with twice as much kinetic energy?

An object hits a wall and bounces back with half of its original speed.What is the ratio of the final kinetic energy to the initial kinetic energy of the object?

A 100-N force has a horizontal component of 80 N and a vertical component of 60 N.The force is applied to a cart on a level frictionless floor.The cart starts from rest and moves 2.0 m horizontally along the floor due to this force.What is the cart's final kinetic energy?

A stone initially moving at 8.0 m/s on a level surface comes to rest due to friction after it travels 11 m.What is the coefficient of kinetic friction between the stone and the surface?

When you drop a pebble from height H,it reaches the ground with speed V if there is no air resistance.From what height should you drop it so it will reach the ground with twice speed?

You carry a 7.0-kg bag of groceries Above the ground at constant speed across a Room.How much work do you do on the bag in the process?

A 10-kg mass,hung by an ideal spring,causes the spring to stretch 2.0 cm.What is the spring constant (force constant)for this spring?

Which requires more work,increasing a car's speed from 0 mph to 30 mph or from 50 mph to 60 mph?

On an alien planet,an object moving at 4.0 m/s on the horizontal ground comes to rest after traveling a distance of 10 m.If the coefficient of kinetic friction between the object and the surface is 0.20,what is the value of g on that planet?

Matthew pulls his little sister Sarah along the horizontal ground in a wagon.He exerts a force on the wagon of 60.0 N at an angle of 37.0° above the horizontal.If he pulls her a distance of 12.0 m,how much work does Matthew do?

A child pulls on a wagon with a force of If the wagon moves a total of In What is the average power delivered by the child?