Question

A runner of mass 56.1 kg starts from rest and accelerates with a constant acceleration of 1.2 m/s^2 until she reaches a velocity of 5.3 m She then continues running at this constant velocity. How long in seconds does the runner take to travel 118 m? A) 19.08 sec B) 24.47 sec C) 53.9 sec D) 15.733333 sec E) 31.152 sec

Answer 1

Option B is the correct answer.

Step-by-step explanation:

Final velocity = 5.3 m/s

Acceleration till 5.3 m/s = 1.2 m/s²

Time taken for this

`t_1=(5.3)/(1.2)=4.42s`

Distance traveled in 4.42 s can be calculated

s = ut + 0.5 at²

s = 0 x 4.42 + 0.5 x 1.2 x 4.42² = 11.72 m

Remaining distance = 118 - 11.72 = 106.28 m

Uniform velocity = 5.3 m/s

Time taken

`t_2=(106.28)/(5.3)=20.05s`

Total time, t = t₁ + t₂ = 4.42 + 20.05 = 24.47 s

Option B is the correct answer.