WEP

An object, initially at rest, is accelerated by a constant force. Which graphs show the variation with time t of the kinetic energy and the variation with time t of the speed of the object?

An object falls from rest from a height h close to the surface of the Moon. The Moon has no atmosphere.

When the object has fallen to height (h/4) above the surface, what is the ratio given in the image?

An increasing force acts on a metal wire and the wire extends from an initial length l0 to a new length l. The graph shows the variation of force with length for the wire. The energy required to extend the wire from l_0 to l is E. The wire then contracts to half its original extension.

What is the work done by the wire as it contracts?

A student of weight 600N climbs a vertical ladder 6.0m tall in a time of 8.0s. What is the power developed by the student against gravity?

A car takes 20 minutes to climb a hill at constant speed. The mass of the car is 1200 kg and the car gains gravitational potential energy at a rate of 6.0 kW. Take the acceleration of gravity to be 10 m/s/s. What is the height of the hill?

The graph shows the variation with distance of a horizontal force acting on an object. The object, initially at rest, moves horizontally through a distance of 50 m. A constant frictional force of 

2.0 N

 opposes the motion. What is the final kinetic energy of the object after it has moved 50

m

?

A motor of input power 160 W raises a mass of 8.0 kg vertically at a constant speed of 0.50 m/s.

What is the efficiency of the system?

A mass is released from the top of a smooth ramp of height 

h

. After leaving the ramp, the mass slides on a rough horizontal surface. The mass comes to rest in a distance d. What is the coefficient of dynamic friction between the mass and the horizontal surface?

* This is a HL question