Exam 8: Potential Energy and Conservation of Energy

As shown in the figure,a 1.45-kg block is held in place against the spring by a 21-N horizontal external force.The external force is removed,and the block is projected with a velocity As it separates from the spring.The block descends a ramp and has a velocity At the bottom.The track is frictionless between points A and B.The block enters a rough section at B,extending to E.The coefficient of kinetic friction between the block and the rough surface is 0.29.The velocity of the block is At C.The block moves on to D,where it stops.How much work is done by friction between points B and C?

A 1500-kg car moving at 25 m/s hits an initially uncompressed horizontal ideal spring with spring constant (force constant)of 2.0 × 10⁶ N/m.What is the maximum distance the spring compresses?

Two frisky otters slide down frictionless hillsides of the same height but different slopes.The slope of the hill of otter 1 is 30°,while the slope of the hill of otter 2 is 60°.If both start from rest,which otter is moving faster when she reaches the bottom of her hill?

Joe and Bill throw identical balls vertically upward.Joe throws his ball with an initial speed twice as high as Bill.If there is no air resistance,the maximum height of Joe's ball will be

A small 1.4-N stone slides down a frictionless bowl,starting from rest at the rim.The bowl itself is a hemisphere of radius 75 cm.Just as the stone reaches the bottom of the bowl,how hard is the bowl pushing on it?

A lightweight object and a very heavy object are sliding with equal speeds along a level frictionless surface.They both slide up the same frictionless hill with no air resistance.Which object rises to a greater height?

A 1,321-kg car climbs a 5.0° slope at a constant speed of 80.0 km/h. Assuming that air resistance may be neglected,at what rate (in kW)must the engine deliver energy to the drive wheels of the car?

A stone is held at a height h above the ground.A second stone with four times the mass of the first one is held at the same height.The gravitational potential energy of the second stone compared to that of the first stone is

A sand mover at a quarry lifts 2,000 kg of sand per minute a vertical distance of 12 m.The sand is initially at rest and is discharged at the top of the sand mover with speed 5.0 m/s into a loading chute.What minimum power must be supplied to this machine?

It takes 87 J of work to stretch an ideal spring from 1.4 m to 2.9 m from equilibrium.What is the value of the spring constant (force constant)of this spring?

On a planet where g = 10.0 m/s² and air resistance is negligible,a sled is at rest on a rough inclined hill rising at 30° as shown in the figure.The object is allowed to move and it stops on a rough horizontal surface,at a distance of 4.0 m from the bottom of the hill.The coefficient of kinetic friction on the hill is 0.40.What is the coefficient of kinetic friction between the horizontal surface and the sled?

A 30-N stone is dropped from a height of 10 m and strikes the ground with a speed of 13 m/s.What average force of air friction acted on the stone as it fell?

At what minimum rate is a 60.0-kg boy using energy when,in 8.00 s,he runs up a flight of stairs that is 10.0-m high?

If a stone is dropped with an initial gravitational potential energy of 100 J but reaches the ground with a kinetic energy of only 75 J,this is a violation of the principle of conservation of energy.

A stone can slide down one of four different frictionless ramps,as shown in the figure.For which ramp will the speed of the ball be the greatest at the bottom?

A toy rocket that weighs 10 N blasts straight up from ground level with an initial kinetic energy of 40 J.At the exact top of its trajectory,its total mechanical energy is 140 J.To what vertical height above the ground does it rise,assuming no air resistance?

If the work done to stretch an ideal spring by 4.0 cm is 6.0 J,what is the spring constant (force constant)of this spring?

Two identical grasshoppers jump into the air with the same initial speed and experience no air resistance.Grasshopper A goes straight up,but grasshopper B goes up at a 66° angle above the horizontal.Which of the following statements about these grasshoppers are correct? (There could be more than one correct choice. )

If a spring-operated gun can shoot a pellet to a maximum height of 100 m on Earth,how high could the pellet rise if fired on the Moon,where g = 1.6 m/s²?

An ideal spring has a spring constant (force constant)of 60 N/m.How much energy does it store when it is stretched by 1.0 cm?