Question

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

• A. 2.5 N
• B. 4.5 N
• C. 3.5 N
• D. 4 N

Answer 1

The correct option is B 4.5 N

Mass of the body, m = 0.9 kg
Initial speed, u = 0
Displacement, s = 250 m
Time, t = 10 s
Using second equation of motion, $s=ut+\frac{1}{2}a{t}^2$
$\Rightarrow 250=0\times 10+\frac{1}{2}a(10{)}^2$
$\Rightarrow 50a=250$
$\Rightarrow Acceleration,a=5m/s^2$
According, to second law of motion:
Force acting on the body, F = ma
$\Rightarrow F=0.9\times 5=4.5N$
Hence, the correct answer is option (2).