Question

The jamaican bobsled team hit the brakes on their sled so that it decelerates at a uniform rate of 0.43 m/s squared how long does it take to stop if it travels 85 m before coming to rest

Answer 1

The distance covered by a certain object which is travelling at a certain speed is calculated through the equation,

     d = (V₀)t + 0.5at²

where d is the distance, V₀ is the initial speed, a is deceleration, and t is the time. Substituting the known values,

    85 = (V₀)(t) + (0.5)(-0.43 m/s)(t²)

Because we are not given with the initial velocity, our answer would remain as the equation which is written above. 

Answer 2

Answer:

Time taken, t = 19.86 seconds    

Explanation:

It is given that,

Deceleration of the sled, a = -0.43 m/s²

We have to find the time it take to stop if it travels 85 m before coming to rest i.e final velocity v = 0. Using third equation of motion as :

$v^2-u^2=2as$

$0-u^2=2\times (-0.43\ m/s^2)\times 85\ m$

u = 8.54 m/s

The initial velocity of the sled is 8.54 m/s. For finding time taken by the sled to stop can be calculated using second equation of motion as :

$s=ut+\dfrac{1}{2}at^2$

$85=8.54t+\dfrac{1}{2}\times (-0.43)t^2$

$0.215t^2-8.54t+85=0$

On solving the above quadratic equation we get, t = 19.86 seconds. Hence, this is the required solution.