1. A 9 kg blob of putty moving at 10 m/s collides with an identical blob of putty at rest and they stick together. What speed do they move off together at?
2. A 25 kg boulder moving at 3 m/s collides with an identical boulder at rest and
they stick together. What speed do they move off together at?
3. A 40 kg girl and a 60 kg boy are both on ice skates. They push off of each other
and the girl moves at 5 m/s. What is the boy's speed?

The focal length of a relaxed human eye is approximately 1.7 cm. when we focus our eyes on a close up object, we can change the refractive power of the eye by about 16 diopters. (a) does the refractive power of our eyes increase or decrease by 16 diopters when we focus closely? explain. (b) calculate the focal length of the eye when we focus closely.

Anybody wanna ? (picture included? )

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.