Force experienced by a tennis ball

[jmgXD6]

A .065-kg tennis ball moving to the right with a speed of 15 m/s is stuck by a tennis racket, causing it to move to the left with a speed of 15 m/s. If the ball remains in contact with the racket for 0.020s, what is the magnitude of the average force experienced by the ball?

F=mv/t I think that's the equation to use.

So if I plug in 0.065 for mass 15 m/s for velocity and .020s for time I would get 48.75 N but that's not an answer choice.

 

[ehild]

The change of the momentum is equal to the impulse: Δ(mv)=FΔt.

The velocity of the ball turns to opposite. How much does its momentum change if the velocity changes from 15 m/s to -15 m/s?

ehild

 

[jmgXD6]

It goes from .975 kgm/s to -.975 kgm/s so it changes by 1.95 kgm/s.

 

[NascentOxygen]

So does that lead to a match with one of the options offered, now?

 

[jmgXD6]

So then if that's the case then 1.95 kgm/s=Ft and t equals .020 I would get 97.5 for force but that isn't an answer choice. What am I doing wrong?

 

[ehild]

97.5 N should be correct.

ehild

 

[jmgXD6]

I feel dumb now, our teacher likes to round and one of the answer choices is 98. Thanks guys.

 

[Office_Shredder]

That's not just rounding, that's the teacher correctly using significant figures