Question

A car with a mass of 800 kg, moving at +15 m/s, crashes head on with a 1500 kg truck moving at -45.5 m/s in the opposite direction. If the two cars become intertwined, with what velocity does the wreckage move?

Answer 1

v = -24.5 m/s

Step-by-step explanation:

Use conservation of momentum P = m*v. Unless there are external forces involved, total momentum must be conserved.

P: momentum

m: mass

v: velocity

1. calculate the total momentum before the collision:

`P=m_(car)v_(car) + m_(truck)v_(truck)`

2. the total momentum after the collision must not change:

`P_(before)=P_(after)`

3. after the collision the velocity of the car is the same as the velocity of the truck:

`v = v_(car) = v_(truck)`

4. combining 2. and 3.:

`P= (m_(car)+m_(truck))v`

5. this equation only has one unknown and can be solved for v:

`v = (P)/(m_(car)+m_(truck)) =(m_(car)v_(car) + m_(truck)v_(truck))/(m_(car)+m_(truck))`

`v=(800*15 + 1500 * (-45.5))/(800 + 1500) = -24.5`