A motorcyclist sees a branch in the road, and hits the brakes, slowing down at -6.42 m/s^2. If it takes him 2.85 s to stop, what was his starting velocity?

his starting velocity was 18.297 ms⁻¹

Explanation:

v = u + at (1)

Where

Final Velocity (v) = 0 ms⁻¹

Initial velocity (u) = ?

Acceleration (deceleration) (a) = -6.42 ms⁻²

time (t) = 2.85 s

Substituting all parameters into equation (1)

0 = u + (-6.42)2.85

0 = u + (-18.297)

0 = u - 18.297

18.297 = u

∴ the initial velocity was 18.297 ms⁻¹

can be answered using momentum.

momentum = p

p1= mass1 * velocity1

p1 = p2

therefore

p1 = 6kg * 4m/s

p1 = 24kgm/s

p2=m2 * v2

24 kgm/s = 7kg * v2

v2 = 24 kgm/s / 7kg

v2= 3.42 m/s