Question

A car is travelling at 72 km/h and is 20m from a barrier when the driver puts on the brakes .The car hits the barrier 2s later.What is the magnitude of the constant deceleration?

Answer 1

Answer:

72km/hr=72×1000(m)/3600(sec)=20m/s=u

v=0

s=20

v^2=u^2+2as where a is acceleration

0=20^2+2a.20

a=-400/40=-10m/s

minus sign shows that it is declaration