A car moving at 50 km/hr skids 20 m with locked brakes. how far will the car skid with locked brakes if it were traveling at 150 km/hr?

The energy to be dissipated is proportional to 1/2 m v^2 ie proportional to v^2 for the same car

In turn F * d = work done.

F is constant (same brakes)

so d is proportional to v^2

if v is multiplied by 3 then d is multiplied by 3^2 = 9

distance = 180m