Question

A block of mass 4 kg slide on a rough surface at t=0 . its speed is 4 m per second it eventually stops after covering a distance of 20cm because of the friction exerted by the surface on it find the work done by the friction

Answer 1

Given,mass(m)=4kg, velocity (v)=4m/s, displacement (s)=20/100=1/5meters, Workdone(w)=1/2mv^2 1/2*4*4^2. =32joules therefore the work done is 32joules

Answer 2

Given that,

Mass of a block, m = 4 kg

Initial speed of the block, u = 4 m/s

Finally it stops, v = 0

Distance, d = 20 cm = 0.2 m

To find,

The work done by the friction.

Solution,

As it finally stops, the block will decelerate. Here, the concept of work-energy theorem will used such that,

$\dfrac{1}{2}m(v^2-u^2)=W$

W is work done by frictional force

$W=-\dfrac{1}{2}\times 4\times 4^2\\\\W=-32\ J$

So, the magnitude of work done by the frictional force is 32 J.

Learn more,

Work-energy theorem

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