A0.140-kg baseball is dropped from rest. it has a speed of 1.20 m/s just before it hits the ground, and it rebounds with an upward speed of 1.00 m/s. the ball is in contact with the ground for 0.0140 s. what is the average force exerted by the ground on the ball during the time of contact?

Light from a sodium lamp passes through a diffraction grating that has 1000 slits per millimeter. the interference pattern is viewed on a screen 1.000 m behind the grating. the first (m = 1) two bright yellow fringes that are visible are 0.7288 m and 0.7300 m from the central maximum. what are the wavelengths of these two fringes?