Intro fo forces

Question

A 1369.4 kg car is traveling at 28.9 m/s when the driver takes his foot off the gas pedal. It takes 5.1 s for the car to slow down to 20 m/s.

How large is the net force slowing the car?

Answer 1

Use Newton's 2nd law.

F = ma = mΔv/Δt

F = m(v₂ - v₁) / Δt

m = 1369.4 kg

v₁ = 28.9 m/s

v₂ = 20 m/s

Δt = 5.1 s

Plug in the numbers and get F in newtons. The negative sign means the force is opposing the direction of motion.