__Question 5.6__:^{–1}to 3.5 m s

^{–1}in 25 s. The direction of the motion of the body remains unchanged. What is the magnitude and direction of the force?

__Solution__:Mass of the body,

*m*= 3 kg

Initial speed of the body,

*u*= 2 m/s

Final speed of the body,

*v*= 3.5 m/s

Time,

*t*= 25 s

Using the first equation of motion, the acceleration (

*a*) produced in the body can be calculated as:

*v*=

*u + at*

∴ a = (v - u) / t

= (3.5 - 2) / 25 = 0.06 ms

^{-2}

As per Newton’s second law of motion, force is given as:

*F*=

*ma*

= 3 × 0.06 = 0.18 N

Since the application of force does not change the direction of the body, the net force acting on the body is in the direction of its motion.

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