Question

A drag racer, starting from rest, speeds up for 402 m with an acceleration of +25.0 m/s/s. a parachute then opens, slowing the car down with an acceleration of -5.95 m/s/s. how fast is the racer moving 325 m after the parachute opens?

Answer 1

After 402 metres the drag reach a maximum speed according the formula: Vf=(Vi^2+2*a*d)^1/2, where Vf is final speed, Vi is initial speed, a is acceleration and d is distance. So then: Vf=(0^2+2*25*402)^1/2=141.77 m/s From that point the drag starts to brake, then with the same formula: Vf=(141.77^2+2*(-5.95)*325)^1/2=127.41 m/s After 325 meter of parachute opens, the drag still moves at 127.41 m/s