A tennis player swings her 1000g racket with a speed of 10 m/s .She hits a 60g tennis ball that was approaching her at a speed of 20 m/s . The ball rebounds at 40 m/s. b. If the tennis ball and racket are in contact for 10 ms, what is the average force that the racket exerts on the ball? How does this compare to the gravitational force on the ball?

Video transcript

Hey, everyone. So this problem is dealing with impulse and momentum. Let's see what it's asking us. A hockey player hits a stationary 200 g puck with a hockey stick of mass 1200 g for 0. seconds. The puck then moves away from the player with a speed of 60 m per second. Determine the average force exerted by the hockey stick on the puck during this contact time. If the seat of the hockey stick was 35 m per second, our multiple choice answers here are a 300 newtons, B 600 newtons, C 400 newtons or D 500 newtons. So this is a pretty straightforward impulse and momentum problem as long as we can recall the impulse momentum theorem. So that theorem states that the force multiplied by the change in time is equal to mass multiplied by the change in velocity. Another way to look at the change in time is the amount of time that that force is exerting. So we are solving for the force so we can rearrange the, the equation to be force multiplied by delta B divided by delta T. And then when we look back into our problem. We have the mass. Now, this is the hockey, we're looking for the force exerted by the hockey stick on the puck. So that will be the mass of the puck. And that was given as 200 g. So I'm gonna rewrite that to keep it in standard units as 0.2 kg. Our change in speed is of the puck, the stationary, so it was originally stationary. So our initial speed was zero, our final speed is 60 m per second. So our change in speed or delta B is 60 m per second. And then our delta T is that time that the force is acting. And so that was given in the problem as 0.2 seconds. So from here it is just a plug and chug where we have the mass of 0.2 kg or delta V of 60 m per second divided by 0.2 seconds. We plug that into our calculator and we get newtons and looking at our multiple choice answers that aligns with answer choice B. So that's all we have for this one. We'll see you in the next video.