Conservation of Momentum of a skydiver

In summary, the conversation is about a physics problem involving a glider and a skydiver. The problem is dealing with the law of conservation of momentum and the confusion lies in handling gravity as an external force. One suggestion is to forget about gravity and focus on the moment when the skydiver drops. It is mentioned that the glider does not change velocity at the instant the skydiver lets go. The conclusion is that there is no impulse acting on the glider and the problem may have been a trick question.
  • #1
James98765
30
0
I reading a physics book on my own right now and I appear to be stuck. The problem is as follows:

A 10 m long glider with a mass of 680 kg (including the passengers) is gliding horizontally through the air at 30 m/s when a 60 kg skydiver drops out by realesing his grip on the glider. What is the glider's velocity just after the skydiver let's go?

The problem is dealing with the law of conservation of momentum. I feel like I understand the concept except this particular problem is confusing me. I have defined the system as glider + skydiver. The problem is that gravity is an external force acting on the system so momentum shouldn't be conserved. I don't quite know how to handle this. If anyone could help me that would be great. Thanks a lot!

-James
 
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  • #2
Forget about gravity. Just worry about the "moment" when the skydiver drops. Hint: How does the momentum of the skydiver change when he let's go?
 
  • #3
That's a good suggestion but I still don't understand one thing. Inorder for there to be a change in momentum their must be an impulse. Because the glider is supposed to gain vertical momentum, wouldn't there have to be a vertical impulse acting on the glider. I don't see how the skydiver letting go could cause I vertical impulse.
 
  • #4
Why do you think the glider is supposed to gain vertical momentum?
 
  • #5
It seems to make sense. If the skydiver is gaining downward vertical momentum shouldn't the glider have to gain upward vertical momentum due to the law of conservation of momentum. I guess that the momentum increase of the skydiver in the down direction is due to an external force (gravity). So that would mean that the glider wouldn't neccessarily have to accelerate upward. Does the glider change momentum in the horizontal direction? If so, where is the impulse in the horizontal direction causing the change?
 
  • #6
James98765 said:
It seems to make sense. If the skydiver is gaining downward vertical momentum shouldn't the glider have to gain upward vertical momentum due to the law of conservation of momentum. I guess that the momentum increase of the skydiver in the down direction is due to an external force (gravity). So that would mean that the glider wouldn't neccessarily have to accelerate upward.
Exactly.
Does the glider change momentum in the horizontal direction? If so, where is the impulse in the horizontal direction causing the change?
What makes you think there's a change in horizontal momentum?
 
  • #7
I think I am coming to the conclusion that the glider doesn't change velocity at all because there is no impulse acting on it. I can't check my answer because it isn't in the book but the conclusion seems valid.
 
  • #8
James98765 said:
I think I am coming to the conclusion that the glider doesn't change velocity at all because there is no impulse acting on it.
You are correct. Neither glider nor skydiver change velocity at the instant he let's go.
 
  • #9
Okay thanks a lot for your help! I think I fell for a trick question from my textbook. I wasn't expecting that. Thanks again! You lead me to a conclusion perfectly!

-James
 

1. What is the conservation of momentum and how does it relate to skydiving?

The conservation of momentum states that the total amount of momentum in a closed system remains constant. In the case of skydiving, the momentum of the skydiver is conserved as they fall through the air, even as their velocity changes due to factors such as air resistance and gravity.

2. How does the mass and velocity of a skydiver affect their momentum?

The momentum of an object is directly proportional to its mass and velocity. This means that a skydiver with a greater mass and/or higher velocity will have a greater momentum as they fall.

3. What happens to the momentum of a skydiver as they deploy their parachute?

When a skydiver deploys their parachute, they experience a sudden increase in air resistance. This causes their downward velocity to decrease, but their momentum remains the same due to the conservation of momentum. As a result, their horizontal velocity increases, allowing them to control their descent and land safely.

4. How does the conservation of momentum explain the physics behind a skydiver landing?

As a skydiver approaches the ground, they increase the force of air resistance by angling their body and using their parachute. This causes their downward velocity to decrease, but their momentum remains the same. As they touch down, their momentum is transferred to the ground, causing them to come to a stop.

5. Can the conservation of momentum be applied to other aspects of skydiving?

Yes, the conservation of momentum can be applied to various aspects of skydiving, such as when a skydiver performs maneuvers in the air or when multiple skydivers come into contact with each other. In all cases, the total momentum of the system remains constant.

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