Apole vaulter uses the pole to lift him to a height of 7 m. what will his velocity be just before he hits the ground? a) 137 m/sb) 34.3 m/sc) 11.7 m/s

Imagine that someone pushes one marble toward a motionless marble. would there still be action-reaction forces involved in the collision? how might the marbles’ motions be changed? ?

How does the kinetic energy of a charge change as the charge moves under the effect of an electric field from higher potential to lower potential? a.the kinetic energy increases.b.the kinetic energy decreases.c.the kinetic energy remains the same.d.the kinetic energy is always zero.

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.