Question

A bike that is coasting down a steep hill increases its speed from 8.0 m/s to 14 m/s. The length of the hill is 55 meters. How much time passes during the descent?

Answer 1

t=5s

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Answer 2

Answer:

Time, t = 5 seconds          

Explanation:

It is given that,

Initial speed of the bike, u = 8 m/s

Final speed of the bike, v = 14 m/s

Length of the hill, d = 55 m

Firstly, we can find the acceleration of the bike. Let it is equal to a. It can be calculated using third equation of motion as :

$a=\dfrac{v^2-u^2}{2d}$

$a=\dfrac{(14)^2-(8)^2}{2\times 55}$  

$a=1.2\ m/s^2$

Let t is the time passes during the descent. It can be calculated using the first equation of motion as :

$t=\dfrac{v-u}{a}$

$t=\dfrac{14-8}{1.2}$      

t = 5 seconds

So, the time passes during the descent is 5 seconds. Hence, this is the required solution.