Question

A constant force acts on a body of mass 0.9 kg at rest for 10s. If the body moves a distance of 250 m, the magnitude of the force is

• A. $3N$
• B. $3.5N$
• C. $4.0N$
• D. $4.5N$

Answer 1

Answer: (D)

$4.5N$

Answer 2

$u = 0,S = 250m,\mspace{6mu} t = 10\sec\mspace{6mu}$

$S = ut + \frac{1}{2}at^{2}$⇒$250 = \frac{1}{2}a\lbrack 10\rbrack^{2} \Rightarrow a = 5m/s^{2}$

So, $F = ma = 0.9 \times 5 = 4.5N$