Mechanics easy question

A car of mass 600kg is brought to rest in 6 seconds from a speed of 20ms^-1.
Neglecting resistances, find the braking force required to achieve this.

okay, m = 600, t = 6, u = 20ms^-1, v = 0ms^-1, a = ?

a = -20/6 = -3.33

Using F = ma
F = 600 x - 3.33 = -2000N

The answer is positive. Is there a way to get to a positive answer or do you just convert it to a +ve number?

Reply 1

Christophicus

hihihihi

I think if you take braking force as positive, you have to take v as negative, making acceleration positive. Braking force will be the same direction as acceleration?

don't you mean u, because v=0 and -0 won't affect anything?

Reply 2

hihihihi

I think if you take braking force as positive, you have to take u as negative, making acceleration positive. Braking force will be the same direction as acceleration?