Question

Cars cruise down an expressway at 25 m/s. Engineers are designing an off-ramp in an interchange with a deceleration of −2.0 m/s2 that lasts 3.0 s.

What velocity will cars have at the end of the off-ramp?

What minimum length should the ramp have?

Answer 1

Answer:

19m/s and 66m

Explanation:

To solve the first part of the question,

Let's use the Ist equation of motion

v = u + at

v = 25 + (-2) * 3 m/s

v = 25 - 6 m/s

v = 19m/s

To solve the second part of the equation

Let's use the second equation of motion

s = ut + 1/2 * at ^ 2

s = 25 * 3 + 1/2 * (-2) * 3 ^ 2

s = 75 - 9

s = 66m  

Answer 2

a) v = u +at

    V = 25 + (-2) x 3 m/s

    v = 25 - 6 m/s

    v = 19m/s

    b) s = ut + 1/2 at²

          = 25 x 3 + 1/2 x (-2) x 3²

          = 75 – 9

          = 66m