00:01
Okay, so here we have a question about work and whether it's positive or negative in certain scenarios.
00:06
So the important thing to know is work done is positive if the applied force has a component in the direction of the displacement.
00:15
So in the direction of the motion of the object.
00:19
So for question one, if the ball is moving upwards, so the ball travels up, does the gravity do positive negative or does gravity? zero work.
00:31
Well, gravity always acts downwards.
00:34
So in this scenario, it's not working in the same direction as the displacement.
00:39
Displacement is upwards, gravity is downwards.
00:41
So this is going to be negative work.
00:49
And we can say that gravity acts against the direction of displacement.
01:10
Okay, and then for two, we are asked to during the same motion, how does the kinetic energy the ball change, that it increased, decrease will stay the same.
01:19
Well, this should be fairly obvious.
01:20
When you chuck something up, it obviously slows down.
01:23
And if it's not caught, it'll slow down, stop, and then come back down again.
01:28
So, k .e...