A tennis ball with a speed of 20.7 m/s is moving perpendicular to a wall. After striking
the wall, the ball rebounds in the opposite
direction with a speed of 13.8276 m/s.
If the ball is in contact with the wall for
0.00828 s, what is the average acceleration of
the ball while it is in contact with the wall?
Take "toward the wall” to be the positive
direction.
Answer in units of m/s2.

The membrane surrounding a living cell consists of an inner and an outer wall that are separated by a small space. assume that the membrane acts like a parallel plate capacitor in which the effective charge density on the inner and outer walls has a magnitude of 7.0 × 10-6 c/m2. (a) what is the magnitude of the electric field within the cell membrane? (b) find the magnitude of the electric force that would be exerted on a potassium ion (k+; charge = +e) placed inside the membrane.

15. give an example for some particles or waves that are moving faster than light in everyday life 16. what is a laser? 17. what is an oscilloscope? 18. what does it means practically that nothing is faster than light in vacuum? 19. what is vacuum?

If an astronaut takes an object to the moon the following is true (choose only one). a the mass will change but the weight will be the same. b both the mass and the weight of the object will be the same. c the weight will change but the mass will be the same. d both the mass and the weight of the object will change.