single vertical slit

using a crowbar to lift a rock is much easeir than lifting it with hands. does this mean that less work is done you use a crowbar to lift the rock than using your bare hands? explain your anwer.

A girl of mass 60 kg throws a ball of mass 0.8 kg against a wall. The ball strikes the wall horizontally with a speed of 11 m/s, and it bounces back with this same speed. The ball is in contact with the wall 0.05 s. What is the average force exerted on the wall by the ball? A) 6600 N B) 26,400...

A 70 kg bicyclist rides his 7.8 kg bicycle with a speed of 14 m/s. How much work must be done by the brakes to bring the bike and rider to a stop? How far does the bicycle travel if it takes 3.5 s to come to rest?

power

Two skaters collide and grab on to each other on frictionless ice. One of them, of mass 66.0 kg, is moving to the right at 2.00 m/s, while the other, of mass 75.0 kg, is moving to the left at 2.80 m/s. What are the magnitude of the velocity of these skaters just after they collide?

A tennis ball is hit into the air and moves along an arc. Neglecting air resistance where along the arc is the speed of the ball at its minimum and maximum? Justify your answer.

Two projectiles are launched from ground level at the same angle above the horizontal, and both return to ground level. Projectile A has a launch speed that is twice that of projectile B. Assuming that air resistance is absent; sketch the trajectory of both projectiles. If the drawings are...

A plane takes off at St. Louis, flies straight to Denver, and then returns the same way. The plane flies at the same speed with respect to the ground the entire flight, and there are no headwinds or tailwinds. Since the earth revolves around its axis once a day, you might expect that the times...

calculating electric potential