A car of mass 1000 kg is travelling at 15 m/s. The driver applies the brakes for 4 seconds, slowing the car to 5 m/s. What is the average power output of the brakes over the 4 seconds? Assume there are no other forces acting on the car.

Kinetic Energy, EK=(1/2)mv2. Energy is conserved, so the work done by the brakes, W, must be equal to the change in kinetic energy of the car, ∆EK. Therefore: W = ∆EK = (1/2)1000(152-52) = 0.51000200 = 100000 = 1*105J. Since power P = W/T, the average power output of the brakes is equal to the total work done by the brakes over the time that the brakes are applied for, therefore: P = 100000/4 = 25000W.

AH
Answered by Adam H. Physics tutor

8530 Views

See similar Physics GCSE tutors

Related Physics GCSE answers

All answers ▸

(IGCSE, Jan 2013, q8 adapted) The astronaut David Scott dropped a hammer and a feather from rest, at the same time and from the same height on the moon. The hammer and the feather landed at the same time. Why?


Explain the motion and forces on a falling object as it approaches terminal velocity.


There is an oil tank that has a rectangular base of dimensions 2.4 m by 1.5 m. The tank is filled with oil of density 850 kg / m3 to a depth of 1.5 m. What is the mass of the oil?


How do I use equations of motion ('suvat') to find a missing quantity?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences