Question

what is the magnitude of the average force required to stop an 1300 kg car in 7.0 s if the car is traveling at 80 km/h ?

Answer 1

Hello there,

1 km/hr = 5/18 m/s

Hence, when 80 km/hr I converted

⇒ 80 × 5/18 m/s = 22.22 m/s

Since finally by applying force we will bring it to velocity of 0 m/s.

⇒v = u + at

⇒0 = 22.22 + a(7)

⇒- 22.22/7 = a

⇒- 3.175 m/s² = a

So, Force = ma

⇒F = 1300 kg × ( - 3.175 m/s² )

⇒F = - 4,127 N

Here negative sign shows that force will be applied against direction of motion.

Hope you find my answer useful.

Harith