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# Kinematcis- ASAP watch

1. A car starts from rest at trffic lights and moves in a straight line. The car moves with constant acceleration 3ms-2 until it is moving with speed 9ms-1. It then moves for 5s with an acceleration of 2ms-2 before moving at a constant speed.
(a) calculate the constant speed reached by the car. Given that the car is still moving at this constant speed 12s after leaving the traffic lights.
(b) calculate the distance travelled in 12s.

Any help is much appriciated, thanks
2. (Original post by beccajonesy)
A car starts from rest at traffic lights and moves in a straight line. The car moves with constant acceleration 3ms-2 until it is moving with speed 9ms-1. It then moves for 5s with an acceleration of 2ms-2 before moving at a constant speed.

(a) calculate the constant speed reached by the car.

Given that the car is still moving at this constant speed 12s after leaving the traffic lights.

(b) calculate the distance travelled in 12s.

Any help is much appriciated, thanks
I'm not going to tell you the answers but I will explain how to get them.

If a car accelerates at a rate of 2ms-2 for 5 seconds from rest how fast is it travelling after 5 seconds?
In other words if the car increases it's speed by 2ms-1 every second for 5 seconds how fast is it travelling afterwards?

Then to get the answer you have to add that to the speed they give you, 9ms-1.

part B is a simple speed = distance/time question

You use the speed you get from part a, and multiply it by the time, 12 seconds, to get the distance covered by the car in the 12 seconds.

If your still not sure, quote me and I'll try and help you.
3. (Original post by insane2642)
I'm not going to tell you the answers but I will explain how to get them.

If a car accelerates at a rate of 2ms-2 for 5 seconds from rest how fast is it travelling after 5 seconds?
In other words if the car increases it's speed by 2ms-1 every second for 5 seconds how fast is it travelling afterwards?

Then to get the answer you have to add that to the speed they give you, 9ms-1.

part B is a simple speed = distance/time question

You use the speed you get from part a, and multiply it by the time, 12 seconds, to get the distance covered by the car in the 12 seconds.

If your still not sure, quote me and I'll try and help you.
Thank you very much, its so much easier when you put it so clear and simple.

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