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A particle of mass 100 g is thrown vertically  upwards with a speed of 5 m/s. The work done by the force of gravity during the time the particle goes up is

Option 1)

0.5 J

Option 2)

–0.5 J

Option 3)

–1.25 J

Option 4)

1.25 J.

Answers (1)

best_answer

As we learnt in:

Net work done by all the forces give the change in kinetic energy -

W=\frac{1}{2}mv^{2}-\frac{1}{2}mv{_{0}}^{2}

W= k_{f}-k_{i}

- wherein

m=mass \: of\: the\: body

v_{0}= initial\: velocity

v= final\: velocity

 

 

 Work done by force of gravity is change in kinetic energy while moving up .

\therefore\ W_{g}=\frac{1}{2}mv_{f}^{2}-\frac{1}{2}mv_{i}^{2}

    W_{g}=0-\frac{1}{2}\times (0.1kg)(25)

    W_{g}=-1.25J


Option 1)

0.5 J

This is an incorrect option.

 

Option 2)

–0.5 J

This is an incorrect option.

Option 3)

–1.25 J

This is the correct option.

Option 4)

1.25 J.

This is an incorrect option.

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