Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

 Jan 30th 2009, 05:55 AM #1 Junior Member   Join Date: Jan 2009 Posts: 1 math A car travels at a uniform velocity of 20 m/s for 5s.The brakes are then applied and the car comes to rest with uniform retardation in a further 8 s.How far does the car travel after brakes are applied????
 Jan 30th 2009, 06:39 AM #2 Banned   Join Date: Jan 2009 Posts: 21 If it has constant deceleration, you can use s=v.t, where v is the average velocity v_avg=(v_init+v_final)/2.
Jan 31st 2009, 12:30 AM   #3
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 Originally Posted by Tabassum A car travels at a uniform velocity of 20 m/s for 5s.The brakes are then applied and the car comes to rest with uniform retardation in a further 8 s.How far does the car travel after brakes are applied????
you can use the formula $\displaystyle a=\frac{v_1-v_0}{t}$
where $\displaystyle v_0= 20$ and$\displaystyle v_1=0$ since its retardation you will get $\displaystyle a$ as negative. Put these values in the formul
$\displaystyle s=v_o.t + \frac{1}{2}.a.t^2$.

Last edited by the curious; Jan 31st 2009 at 12:32 AM.

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