Consider the problem of returning a serve in tennis. a serve is hit at a speed of 67.7 m/s, and is hit back to the server with a speed of 40.8 m/s. the ball of mas m = 57 g is in contact with the racket for 0.01s.
(a) what is the magnitude of the impulse imparted to the ball as it is returned to the server?
(b) estimate the magnitude of the average force on the ball.

I'm thinking it's 2 you are asked to explain the earth's magnetic field. which is the best reply? 1. the earth's magnetic south is similar to the north pole of a magnet. 2. the earth's core has a strong magnetic charge similar to the south pole of a magnet. 3. the earth's geomagnetic south is similar to the south pole of a magnet. 4. the earth's magnetic charge is not centered at either pole; it varies based on location.

Consider a hydrogen atom in the ground state. what is the energy of its electron? =e= jj now consider an excited‑state hydrogen atom. what is the energy of the electron in the =5n=5 level? =e5= j

For waves in the ocean, the medium of the waves is a. air b. water c. energy d. a passing boat