The highest speed ever achieved on a bicycle was reached by John Howard of the United States. The bicycle, which was accelerated by being towed by a vehicle, reached a velocity of +245km/h. Suppose Howard wants to slow down, and applies the breaks on his now freely moving bicycle. If the average acceleration of the bicycle during braking is -3.0 m/s^, how long will it take for the bicycles velocity to decrease by 20.0 percent?

Explanation:

The motion of a projectile consists of two independent motions:

- A uniform motion along the horizontal direction (constant velocity)

- A uniformly accelerated motion along the vertical direction (constant acceleration)

The time of flight of a projectile is given by

where

is the initial vertical velocity

is the acceleration due to gravity

Here the time of flight is

t = 8 s

So, the initial vertical velocity is:

At the same time, the horizontal distance covered by the projectile is given by

where

is the horizontal velocity, which is constant

t is the time of flight

Here we know that the range of the projectile is 0.3 km, so

d = 0.3 km = 300 m

So the horizontal velocity is

Therefore, we can find the angle of projection of the projectile by using: