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# M1 help :) watch

1. So it would appear that I am shocking at mechanics and this may be a struggle. I can't seem to do question 11?
Like for part a I worked out the acceleration of both the forces using f=ma. Then just took the larger acceleration from the smaller and got 0.33ms^-2 which is the right answer. No clue if that is how you do it?

I don't understand part b? Can someone help me with that

Thanks
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2. (Original post by Super199)
So it would appear that I am shocking at mechanics and this may be a struggle. I can't seem to do question 11?
Like for part a I worked out the acceleration of both the forces using f=ma. Then just took the larger acceleration from the smaller and got 0.33ms^-2 which is the right answer. No clue if that is how you do it?

I don't understand part b? Can someone help me with that

Thanks
For the first part, since the speed is constant then the resistance to motion must equal the driving force. When the driving force is increased the resistance will be the same initially and so the initial acceleration is simply that produced by the extra driving force.
For part (b) since the resistance is proportional to the speed then we must have R=kv. so find the value of k by using the fact that the resisatnce is 870 when the speed is 15 and then use that value of k to find the resistance when the speed is 20. Finally use Newtons second law to obtain the acceleration.
3. (Original post by brianeverit)
For the first part, since the speed is constant then the resistance to motion must equal the driving force. When the driving force is increased the resistance will be the same initially and so the initial acceleration is simply that produced by the extra driving force.
For part (b) since the resistance is proportional to the speed then we must have R=kv. so find the value of k by using the fact that the resisatnce is 870 when the speed is 15 and then use that value of k to find the resistance when the speed is 20. Finally use Newtons second law to obtain the acceleration.
I got the resistance to the motion to be 1160N. F=ma. So a=f/m. A=1160/1000?
4. (Original post by Super199)
I got the resistance to the motion to be 1160N. F=ma. So a=f/m. A=1160/1000?
You should have driving force-resistance = ma. You have not taken the driving force into consideration.

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