Question

A car (mass 1200 kg, speed 100 km/h) and a truck (mass 2800 kg, speed 50 km/h) are moving in the same direction along a highway. If the car slams into the truck from behind and the two vehicles remain locked, what is the speed of the wreck immediately after the collision?

Answer 1

Answer:

Speed of the wreck after the collision is 65 km/h

Explanation:

When a car hits truck and sticks together, the  collision would be totally inelastic.  Since the both the vehicles  locked  together, they have the same final velocity.

Mass of car  $m_{1}=1200 kg$

Mass of truck $m_{2}=2800 kg$

Initial speed of the car $u_{1}=100 km /h$

Initial speed  of the truck $u_{2}=50 km /h$

The final velocity of the wreck will be

$m_{1}u_{1}+m_{2}u_{2}=m_{1}v_{1}+m_{2}v_{2}$

since final speed are same, $v_{1}=v_{2}=v$

$m_{1}u_{1}+m_{2}u_{2}=(m_{1}+m_{2})v$

$1200\times 100 +2800 \times 50 =(1200+2800)v\\v=\frac{260000}{4000} \\v=65 km/h$