Question

A bus driver makes an emergency stop by slamming on the bus's brakes. Later, he slams on the brakes

Answer 1

Answer: Option C

Explanation: Let's do a heavy simplification.

The kinetic energy of the bus is K = (m/2)*v^2

Where m is the mass of the bus, and v is the velocity of the bus.

When the brakes are used, we can do a linear relationship that gives us the distance that the bus needs to come to a full stop, and this will depend on the kinetical energy that the buss had just right before, so the distance that the bus moves after slamming on the brakes is:

D = K/F = ((m/2)*v^2)/F

Where F depends on the effectiveness of the brakes, as bigger F is, faster the bus comes to a full stop.

Now, if we double the velocity; we have:

D' = ((m/2)*(2*v)^2)/F = ((m/2)*4*v^2)/F = 4*(((m/2)*v^2)/F) = 4*D

D' = 4D

So the distance is quadrupled, then the correct option is C

Answer 2

C. The stopping distance is quadrupled