Arocket sled used in old air force test could accelerate a volunteer at rates of 90m/s^2. with this acceleration being constant, how long would it take for one of these rocket sleds to travel the length of a one kilometer test track if it starts from rest? a) 11.1sec b) 22.2sec c)4.71sec d) 32.2sec

option (c) 4.71 seconds

Explanation:

Given:

Distance to be covered = 1 km = 1000 m

Acceleration, a = 90 m/s²

From Newton's equation of motion

where,  

s is the distance

u is the initial speed  = 0 m/s ( since it starts from rest )

a is the acceleration

t is the time

on substituting the respective values, we get

or

45t² = 1000

or

t² = 22.22

or

t = 4.71 seconds

Hence, the correct answer is option (c) 4.71

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