Answer to Question #129272 in Physics for Lg

Question

Car travels 72km/hr in 5 sec find acceleration and distance travelled? If car takes 2.5 seconds to stop calculate the new acceleration and find the distance a car takes to stop

Answer 1

$v_0=0$; $72(km/hr)=20(m/s)$

(a)

$v=at\to a=v/t=20/5=4(m/s^2)$

$S=at^2/2=4\cdot5^2/2=50(m)$

(b)

$v_0=20(m/s)$

$v=v_0-at\to a=v_0/t=20/2.5=8(m/s^2)$

$S=\frac{v^2-v_0^2}{2a}=\frac{20^2}{2\cdot8}=25(m)$