Is average force dependent on the exertion time of force?

In summary, the man exerts a average force of 9.81 Newtons when jumping at a velocity of 1.8 meters per second.
  • #1
dawningparadox
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Homework Statement


A 65 kg man jumps at a velocity of 1.8 m/s. The contact time is 0.45 seconds. Find the average force exerted by the man.

Homework Equations


F=ma+mg

The Attempt at a Solution


F=65*(1.8/.45)+65*9.81

I'm not sure if the equation has to be divided by the contact time, .45 seconds, to obtain the average force acting on the man.
 
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  • #2
Hint: Think in terms of momentum changes.
 
  • #3
dawningparadox said:

The Attempt at a Solution


F=65*(1.8/.45)+65*9.81

I'm not sure if the equation has to be divided by the contact time, .45 seconds, to obtain the average force acting on the man.
You did divide by the time. Are you just asking whether that was the right thing to do? Yes, it is, and I agree with your answer.
You don't explain how you came up with that equation. I'm guessing that you divided the velocity change by the duration to obtain the average acceleration. If so, you are quite right that mass times average acceleration gives average force.
Doc Al's hint gives you another route to the same answer.
 
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Likes Doc Al
  • #4
Yeah, I should have just said "yes". :smile:
 
  • #5
haruspex said:
You did divide by the time. Are you just asking whether that was the right thing to do? Yes, it is, and I agree with your answer.
You don't explain how you came up with that equation. I'm guessing that you divided the velocity change by the duration to obtain the average acceleration. If so, you are quite right that mass times average acceleration gives average force.
Doc Al's hint gives you another route to the same answer.

Sorry for the ambiguity in my question. I'm well aware that we have to divide the velocity by contact time to obtain the average acceleration. What really confuses me is that due to the fact that the man also has to provide mg in 0.45 seconds, alongside ma which was solved above, do i also have to divide mg by 0.45 seconds to find out the AVERAGE force provided by the man, which unit is 1 second? Please correct me if there is any misconception.
 
  • #6
dawningparadox said:
Sorry for the ambiguity in my question. I'm well aware that we have to divide the velocity by contact time to obtain the average acceleration. What really confuses me is that due to the fact that the man also has to provide mg in 0.45 seconds, alongside ma which was solved above, do i also have to divide mg by 0.45 seconds to find out the AVERAGE force provided by the man, which unit is 1 second? Please correct me if there is any misconception.
The mg is constant over the time period, so it must equal its own average. If you divide it by time it will no longer be a force, but something rather strange... mass times jerk, I guess.
 
  • #7
haruspex said:
The mg is constant over the time period, so it must equal its own average. If you divide it by time it will no longer be a force, but something rather strange... mass times jerk, I guess.

Thanks.
 

1. How is average force affected by the exertion time of force?

The average force is directly proportional to the exertion time of force. This means that as the exertion time increases, the average force also increases. Similarly, as the exertion time decreases, the average force decreases.

2. Is there a limit to the relationship between average force and exertion time?

Yes, there is a limit to this relationship. The limit is determined by the physical capabilities of the object exerting the force. Once the exertion time reaches a certain point, the object may not be able to maintain the same level of force, resulting in a decrease in average force.

3. Does the type of force being exerted affect the relationship between average force and exertion time?

Yes, the type of force can have an impact on this relationship. For example, if the force being exerted is a constant force, the average force will be directly proportional to the exertion time. However, if the force is a variable force, the relationship may not be as straightforward.

4. Can the average force and exertion time be manipulated to achieve a desired outcome?

Yes, the average force and exertion time can be manipulated to achieve a desired outcome. This can be done by adjusting the intensity and duration of the exertion, which can impact the average force exerted.

5. Are there any other factors that can affect the relationship between average force and exertion time?

Yes, there are other factors that can influence this relationship, such as the angle of force, the mass of the object exerting the force, and the surface on which the force is being exerted. These factors can alter the amount of force needed to achieve a certain outcome and therefore impact the relationship between average force and exertion time.

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