A bicycle with 0.80 m diameter tires is coasting on a level road at 5.6 m/s. A small blue dot had been painted on the tread of the rear tire. What is the speed of the blue dot when it is 0.4m above the road.

the speed of the blue dot when it is 0.4m above the road is 7.92 m/s

Explanation:

If the blue dot is 0.4m above the road, then it is at exactly half of the tire diameter. Thus, the vertical component on the velocity (Vj) = 5.6 m/s and the horizontal component of the velocity(Vi) is 5.6 m/s.

V = (5.6i + 5.6j)

From vector laws, the magnitude of the vector becomes;

Therefore, the speed of the blue dot when it is 0.4m above the road is 7.92 m/s