10 on earth a ball is dropped and falls 20 m in a vacuum the...

10. On Earth, a ball is dropped and falls 2.0 m in a vacuum. The acceleration of the ball at 1.0 m is 10 m / s2. 0 m The Ball is right here 0.5 m goes down 1.0 m 1.5 m 2.0 m What is the acceleration of the ball at 0.5 m? A 5.0 m / s2 B 10 m / s2 C 15 m / s2 D 20 m / s2 11. A skydiver reaches terminal velocity. Then he opens his parachute. What happens to the skydiver as the parachute opens? A There is a decrease in weight. B There is acceleration upwards. C There is an increase in speed. D There is movement upwards.

Transcript

00:01 Okay, in this first question, we have a ball which is falling down in a vacuum.

00:05 And we are asked, what's the acceleration of the ball at 0 .5 meters? well, if we think about the equation f is equal to m .a.

00:14 And also the equation weight is equal to mg.

00:17 These two are the same equations.

00:19 Weight is a force.

00:21 And the acceleration due to gravity on earth, we just label g.

00:25 And in this question, g is just 10.

00:27 The actual value is closer to 9 .81.

00:30 Round it to 10 metres per second squared.

00:33 Now this means that anything which falls on earth will accelerate with a value of 10 metres per second squared.

00:41 And the only way that acceleration gets reduced is due to air resistance.

00:45 So the force downwards will be reduced if there is air resistance by an opposing force upwards that will increase as the ball falls faster and it will eventually match the weight of the ball.

00:58 However, if there is no air resistance, that means there is no force upwards.

01:04 That means the force will just remain as the weight, which is going to be a constant, and that means the acceleration due to gravity will be a constant, or the acceleration will be a constant because it's just going to stay the acceleration due to gravity.

01:16 So that will always be 10, so we can say at 0 .5 meters, acceleration equals 10 meters per second squared.

01:26 10 meters per second squared.

01:29 In the next part, we have a skydiver who is accelerating down, due to their weight, mg, but now they open up a parachute.

01:40 And what happens then? so, a, is there a decrease in weight? well, no, there can't be.

01:46 Okay, there's a skydiver plus the parachute.

01:48 That weight will remain the same.

01:50 It will remain a constant...