00:01
Hello, here a football player whose mass is 110 kilograms is running at the initial speed of 9 .5 meters per second.
00:13
And then he catches a ball which is 0 .41 kilograms heavy and has the initial speed of 22 .5 meters per second.
00:31
First, we have to calculate the final speed of the player if the initial speed of the player and initial speed of the ball are in the same direction.
01:01
So here, mass of the player times his initial speed plus mass of the ball times its initial speed plus mass of the ball times its initial speed equals to the total mass divided by final speed therefore final speed equal to product equals to the initial momentum divided by total mass which is 110 kilograms times 9 .5 meters per second plus 0 .41 kilograms times 22 and a half meters per second and that is divided by 110 kilograms plus 0 .41 kilograms.
02:23
That is 955 meters per second.
02:46
So now let's answer question 2, where we have to calculate the change in kinetic energy.
02:56
So this change equals to the initial kinetic energy which is, sorry, to the final kinetic energy, which is m1 plus m player plus m ball, times the final ball squared minus mass of the player times initial speed of the player squared minus mass of the ball times initial speed of the player squared minus mass of the ball times initial speed of the ball squared.
03:31
Let's calculate it.
04:38
That is 34, negative 34 and half joules.
04:43
So that's the answer to question two.
04:47
Now let's answer question 3 and 4.
04:49
And to do this, i have to clean up the screen.
05:13
Now the initial speeds are in the opposite direction...