Question

A truck initially traveling at 20m/s decelerated at 1.50m/s2. Find (a) how long it takes to stop (b) how far it moves in that time and (c) how far the truck moves in the third second after the brakes are applied

Answer 1

vf² = vi² + 2ad

vf = vi +at

vf = final velocity

vi = initial velocity

decelerated = a = - (negative)

a. stop ⇒ vf = 0

vf = vi+at

0 = 20 - 1.5t

1.5t=20

t = 13.3 s

b. vi = 20 m/s

0 = 20² - 1.5d

1.5d = 20²

1.5d = 400

d =266.67 m

c. d = vi.t -1/2at²

d = 20.3 - 1/2.1.5.3²

d = 53.25 m