Question

A constant force acting on a body of mass of 5 kg change its speed from $5ms^{- 1}$to $10ms^{- 1}$in 10 s without changing the direction of motion. The force acting on the body is :

• A. 1.5 N
• B. 2 N
• C. 2.5 N
• D. 5 N

Answer 1

Answer: (C)

2.5 N

Answer 2

Here $m = 5kg,u = 5ms^{- 1},v = 10ms^{- 1},t = 10s$

Using $v = u + at$

$a = \frac{v - u}{t} = \frac{(10 - 5)ms^{- 1}}{10s} = 0.5ms^{- 2}$

As $F = ma$

$\therefore F = (5kg)(0.5ms^{- 2}) = 2.5N$