A57 g tennis ball is traveling at 45 m/s to the right, when it hits a racket. the ball reversed direction and travels at 33 m/s. the ball is in contact with the racket for 0.0085 s.

what is the magnitude of the force that was exerted on the ball?

a. 1.8n
b. 12n
c. 81n
d. 520n

D. 520 N

Explanation:

According to the impulse theorem, the change in momentum of the ball is equal to the impulse exerted on the ball, mathematically:

where

is th change in momentum

F is the average force exerted on the ball

is the time of contact

The change in momentum of the ball is

where

m = 57 g = 0.057 kg is the mass of the ball

u = 45 m/s is the initial velocity

v = -33 m/s is the final velocity (in the opposite direction)

Substituting,

The time of the collision is

Therefore, the average force is

So, the magnitude is approximately 520 N.

answer; (d) spontaneous processes are characterized by the overall conversion of order to disorder;

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.