Question

A Mack truck and a Honda traveling at the same speed have a head-on collision. The vehicle to undergo the greater change in velocity will be the

A) Mack truck

B) Honda

C) both the same

I was going to choose answer C, but i realized it wasnt asking about which had greater force, but asking greater change in velocity.

Answer 1

Correct Option: B) Honda

Imagine a big truck colliding head-on with a car, we expect the truck to keep moving in the same direction and the car to stop or being dragged by the truck. So, we expect the less massive car to undergo the greater change in velocity.

We can prove our intuition to be true with mechanics. Let M be the mass of Mack truck and m be the mass of Honda. We assume that the Mack truck is more massive than the Honda (M>m)

According to Newton's third law of motion, the force applied by the Honda on Mack is equal in magnitude and opposite in direction to the force applied by the Mack on the Honda.

By Newton's second law, the acceleration of Mack is

the acceleration of Honda is

Since M>m

The acceleration of the less massive Honda is greater than the acceleration of the more massive Mack. Acceleration is the rate of change of velocity. Therefore, Honda undergo the greater change in velocity.