NotYourType
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Need help with the following
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NotYourType
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Help with 6)a)ii
And 10) b)
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Kevin De Bruyne
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(Original post by NotYourType)
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Help with 6)a)ii
And 10) b)
For 6aii it may help for you to draw a diagram with all the forces and then resolve them. It may help for you to to think about what you did in part i) and how the opposing force changes your answer.

For 10 b I'm not so sure, but what would you think the effect is of bending your knees? How does that tie in with Newton's 2nd law?
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NotYourType
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(Original post by SeanFM)
For 6aii it may help for you to draw a diagram with all the forces and then resolve them. It may help for you to to think about what you did in part i) and how the opposing force changes your answer.

For 10 b I'm not so sure, but what would you think the effect is of bending your knees? How does that tie in with Newton's 2nd law?
hmm..okay , thank you anyway for trying
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Kevin De Bruyne
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(Original post by NotYourType)
hmm..okay , thank you anyway for trying
Hopefully you kinda understood my hint for 6aii.

Also for 10, b)i leads on to b)ii. What do you think will happen to the time of impact? What does that say about the variable in F=ma?
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NotYourType
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(Original post by SeanFM)
Hopefully you kinda understood my hint for 6aii.

Also for 10, b)i leads on to b)ii. What do you think will happen to the time of impact? What does that say about the variable in F=ma?
i did try out the drawing for the 6th one ,but kinda messed up with the answers
and for the 10th one, apparently bracing your knees increases time ,but i don't get why!
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Kevin De Bruyne
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(Original post by NotYourType)
i did try out the drawing for the 6th one ,but kinda messed up with the answers
and for the 10th one, apparently bracing your knees increases time ,but i don't get why!
It would be helpful if you could show some working for q 6

And to be honest for the 10th one, you don't really need to know/explain why bracing your knees increases time.

For bi you just need to follow your intuition 'it increases time' and no explanation needed.

For bii you just need to use bi and explain why it corresponds less of a force. Can you see why?
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NotYourType
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This is the diagram I drew...my car looks so funny
Turns out my answer for a)ii) is wrong..
Apparently , you're supposed to add 1650 and 600
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_Caz_
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have you got it sorted now?
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NotYourType
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(Original post by _Caz_)
have you got it sorted now?
I still don't get why we have to add those both together :/
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uberteknik
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(Original post by NotYourType)
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Help with 6)a)ii
And 10) b)
10. b ii)

Newton's second law states that the acceleration of an object is proportional to the applied force vector. i.e. it acts in the same direction as the force but is inversely proportional to its mass.

In other words a = \frac{F}{m}

making Force the subject produces the more familiar:

F = ma

Applying this to the legs extended vs bent problem:

On contact with the ground, the body will be subjected to a deceleration and therefore the force applied to the rigid bones and soft tissue of the person will be a product of the bodies mass and how quickly any part of the body decelerates.

If the legs are extended and rigid, deceleration will act almost all vertically through the length of the leg bones with little or no horizontal motion. Deceleration will be rapid because the bones cannot compress or move.

Since acceleration is the rate of change of velocity, and velocity is distance moved in a given time, then the velocity must change rapidly because there is no ability to move. Hence the force applied to the bones because of the rapid deceleration all in the same direction will be very high. This deceleration force may easily be enough to stress bones and joints to fracture and breaking.

If the legs are bent, then the muscles of the body can absorb the deceleration by converting kinetic energy into heat. The deceleration will no longer all be in the vertical direction but will be a vector sum of the leg motion both horizontal and vertical. Since the legs are able to move freely, the rate of change of velocity is reduced and hence the body and bones will be subjected to a much reduced force able to withstand the impact.
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_Caz_
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(Original post by NotYourType)
I still don't get why we have to add those both together :/
Does this help? for 6aii

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NotYourType
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(Original post by _Caz_)
Does this help? for 6aii

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omg ,yes ! Thank you so much...
I have way more questions to clarify..But I'm scared that ppl might get annoyed
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(Original post by NotYourType)
omg ,yes ! Thank you so much...
I have way more questions to clarify..But I'm scared that ppl might get annoyed
If you post them I'll have a go of a few if you want.

The trick to questions like these is drawing diagrams - if something changes in the situation, draw a new diagram. the F in f=ma is the resultant force so is the net force on the object. so you have to pick a direction as positive and then add those up and take the ones in the opposite direction as negative. Then you put all that equal to the mass multiplied by acceleration.
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NotYourType
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Please help with the 5th question and the past paper one
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