Question: On an object of mass 1 kg moving along x-axis with constant speed 8m/s, a constant force 2 N is applied in positive y- direction. Find its speed after 4 seconds.

Please explain how to solve the above question. The answer is 8√2m/s.

Here,

Speed along X axis is, v_{x} = 8 m/s

Mass, m = 1 kg

Force applied, F_{y} = 2 N

Acceleration, a_{y} = F/m = 2/1 = 2 m/s^{2}

Now, along Y the body starts moving after application of the force.

Initial velocity along Y, u_{y} = 0

So, using, v = u + at

=> v_{y} = u_{y} + a_{y}t

=> v_{y} = 0 + (2)(4)

=> v_{y} = 8 m/s

So, magnitude of the resultant velocity is,

v = (v_{x}^{2} + v_{y}^{2})^{1/2} = (8^{2} + 8^{2})^{1/2} = 8√2 m/s

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