<PRE><B>Question 878535</B>
A car of mass 1000 kg moving with a velocity of 36 km/h collides with a tree and come to in rest in 5 sec. what will be the force exerted by the car on the tree.
mass of car  m= 1000 kg 
velocity (initial speed ) U = 36km/h (by converting into m/s )
=36x5/18=10 m/s 
final speed  V=0
we know  V=U +at
        0= 10 +ax5
-10/5 =-2m/s retardation ( negative acceleration is known as retardation)
Force = mass x acceleration 
force =1000x2 =2000 kg-m/s^2 
 </PRE>