Question

A 1200 kg car moving north at 50 km/h collides with a 1600-kg car moving east at 30 km/h. The cars stick together, and the wreckage moves off at an initial speed of
a. 27 km/h
b. 38 km/h
c. 39 km/h
d. 58 km/h
*follow up question
• The direction in which the wreckage of he preceding collision moves off is
a. 39° E of N
b. 45° E of N
c. 51° E of N
d. 54° E of N

Answer 1

@asya here it is given that the cars stick to each other after the collision. So, this is a n inelastic collision. In an inelastic collision, can you tell me quantities that are conserved?

Answer 2

total energy and momentum.

Answer 3

only momentum in case of inelastic collision.

Answer 4

apply the conservation of momentum you will get the ans. of first part.

Answer 5

total energy will remain always conserved for any isolated sysetm.

For Elastic collision conserved quantities are:
1. Kinetic energy
2. Momentum
3. Total energy

For Inelastic collision conserved quantities are:
1. Momentum
2. Total energy.

Answer 6

okay. in that frame of reference yes. total energy.

Answer 7

i mean context

Answer 8

For Determining direction:

You know P1(momentum of 1st particle), P2(momentum of 2nd particle) and P (final momentum)

then apply the triangle/parallelogram law of vector addition

Answer 9

@chand Even in this context both quantities are conserved but we don't need total energy for our answer.

Answer 10

right. when you were saying total energy, i thought you were referring to total mechanical energy(potential and kinetic). so i just got confused there.