A ball of mass 4.0 kg moving with an initial velocity of 2.0 m/s to the right collides elastically with another ball of mass 6.0 kg moving with a
velocity of 4.0 m/s to the left. After the collision, the first ball is moving
with a velocity of 5.2 m/s to the left. What is the velocity of the second
ball after the collision?

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.

What is the coefficient of kinetic friction μk between the block and the tabletop?

What is the thinnest soap film (excluding the case of zero thickness) that appears black when illuminated with light with a wavelength of 480 ? the index of refraction of the film is 1.34, and there is air on both sides of the film. express your answer in nanometers. hint 1. how to approach th