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M1 kinematics question

'A car is being driven along the road at a steady 25ms-1 when the driver suddenly notices that there is a fallen tree blocking the road 65m ahead. The driver immediately applies the brakes giving the car a constant retardation of 5ms-2. A) How far in front of the tree does the car come to rest? B) If the driver had not reacted immediately and the brakes were applied one second later, with what speed would the car have hit the tree?'
I've solved part A and gotten 2.5m but I'm not sure how to solve part B. I've tried using 't+1' as the time in the constant acceleration equations but I don't seem to be getting anywhere with it

(edited 8 years ago)

Reply 1

Student403

In one second the car travels 25m because its speed is 25ms^-1. So why don't you try solving by taking away 25m from the distance when he notices the tree? That would provide you with s, you have u, you want v, and you have a