Question

A car weighing 4000kg travelling of 25km/sec stops in 5sec by declerating uniformally,then it's retardation is

Answer 1

Applying 1st law of motion
v=u+at
v=0
u=25km/s
t=5 s

0=25+5a
-25=5a
a=-25/5
a=-5 km/sec
Therefore retardation=5km/sec²