Question

If 250 J of work is done in sliding a 5 kg block up an inclined plane of height 4m. Work done against friction is

Answer 1

For calculating work done when friction is involved,
Total work done(W)=Work done against friction(W1) + Work done against gravity(W2)
Given:
Total work done(W)=250J
Mass(m) = 5kg
Therefore Weight(w)=5*9.8=49N
Height(h)=4m

W=W1+W2
W=W1+(w*h)
250=W1+(49*4)
W1=250-196
W1=54
Hence work done against friction is 54J

Answer 2

m=5 kg

g=10 m/s^2

h=4 m

Work done, W=250 J

When there is no friction, then

Work done, Wo=mgh

Wo=5×10×4=200 J

Work done against friction, Wf=W−Wo

Wf=250−200=50 J

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