Question

A policeman starts from rest to catch a thief
running at a constant speed of 20 m/s. With how
much acceleration must the policeman run to
catch the thief in 5 seconds? (Initial they were at
same position very close to each other)
(1) 20 m/s2
(2) 16 m/s2
(3) 4 m/s2
(4) 8 m/s2​

Answer 1

Answer:

(1) 16 m/s^2

Explanation:

Formula for distance traveled in nth second, s = u +a/2(2n-1)

Given, distance travelled in 8th second = 120m

And u= 0m/s [ Object starts from rest ]

So, n = 8 and s =120, put values in the formula

120 = 0 + a/2[2(8)-1]

120 = a/2(16-1)

120 = a/2(15)

a = 120 *2/15 = 8*2 = 16

so acceleration = 16m/s^2