Question

A bicyclist in the Tour de France crests a mountain pass as he moves at 18 km/h. At the bottom, 3.8 km farther, his speed is 85 km/h. What was his average acceleration (in m/s2) while riding down the mountain?

Answer 1

Initial speed, u = 18 km/h
Final speed, v = 85 km,/h
Distance traveled, s = 3.8 km

Note:
1 km/h = 0.27778 m/s
Therefore
u = 18*0.27778 = 5 m/s
v = 85*0.27778 = 23.61 m/s
s = 3.8 km = 3800 m

Let a = the acceleration.

Use the formula
v² = u² + 2as, or
a = (v² - u²)/2s
= (557.493 - 25)/7600
= 0.07 m/s²

Answer: 0.07 m/s²