Question

a 2000kilograms truck is braked to a top in 15meters from an initial speed of 12meters per second . how much force was required ?

Answer 1

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Answer 2

F = ma --> a = F/m

v^2 = u^2 + 2as <--- kinematic equation

Substitute a=f/m into kinematic equation

v^2 = u^2 + 2s x F/m.

Final velocity v equals 0 to fit the equation to the problem
u = 12 (m/s)
s = 15 (m)

0^2 = 144 + (2 x 15) x (F/2000)

(-144 / 30) x 2000 = F

therefore F = -96000.

The negative means that the force opposite to truck's motion, i.e in the opposite x direction.