An electric vehicle starts from rest and accelerates at a rate of 2.4 m/s2 in a straight line until it reaches a speed of 27 m/s. The vehicle then slows at a constant rate of 1.3 m/s2 until it stops. (a) How much time elapses from start to stop? (b) How far does the vehicle move from start to stop?

Question

Prego

Physics

22 June, 16:58

An electric vehicle starts from rest and accelerates at a rate of 2.4 m/s2 in a straight line until it reaches a speed of 27 m/s. The vehicle then slows at a constant rate of 1.3 m/s2 until it stops. (a) How much time elapses from start to stop? (b) How far does the vehicle move from start to stop?

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Kash Buckley · Answer 1

A) use v=u+at for both

First section, v=27, u=0, a=2.4. You should get 11seconds.

Second section, v=0, u=27, a=-1.3. You should get 21seconds.

This means that the total time is 22seconds.

b) You can either use s=ut+0.5at^2 or v^2=u^2+2as. Personally, I would use the second one as you are not relying on your previous answer.

First section, v=27, u=0, a=2.4. You should get 152m.

Second section, v=0, u=27, a=-1.3. You should get 280m.

This makes your overall displacement 432m.