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July 26, 2025, 04:08:29 am

Author Topic: Need help!!  (Read 713 times)  Share 

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madoscar65

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Need help!!
« on: January 02, 2011, 07:05:32 pm »
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Hi People,

A dodgem car of mass 200kg is driven south into a rigid barrier at an initial speed of 5.0m/s and the dodgem rebounds at a speed of 2.0m/s, it is in contact with the barrier for 0.2s. Calculate the average acceleration of the car during its interaction with the barrier.

Thanks !!
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kamil9876

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Re: Need help!!
« Reply #1 on: January 02, 2011, 07:41:33 pm »
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Just use the definition of average acceleration.

Let us take south as positive.



So that means the direction is north as we have taken south as positive.
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QuantumJG

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Re: Need help!!
« Reply #2 on: January 02, 2011, 07:47:00 pm »
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Ok so u = 5m/s & v = -2m/s (depending on which way you define as positive and negative)

v = u + at

So,

-2 = 5 + 0.2a

-7 = 0.2a

a = -35ms-2

So what was the problem?

I just want to add:

Kamil is more precise in how she? took on the problem as that is the definition of average. In VCE physics though, our suvat (distance, initial velocity, final velocity, acceleration & time) formulas deal with acceleration being constant and in a realistic case they give you the average. If you want to deal with non-constant acceleration you need to deal with calculus (which you can easily use to derive the suvat formulas).


« Last Edit: January 02, 2011, 08:00:03 pm by QuantumJG »
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madoscar65

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Re: Need help!!
« Reply #3 on: January 02, 2011, 09:38:16 pm »
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I also got the same answer as you which is 35m/s^2, but the answer says 3.5m/s^2... , I thought I must have done something wrong. But it appear to be the back of the book that is wrong.. Problem all solved now. Thanks :)
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bomb

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Re: Need help!!
« Reply #4 on: January 03, 2011, 01:52:56 am »
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Yeah I remember doing that question last year haha, the back of the book is wrong :)
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