Physics, 19.07.2019 08:20 xxxamslashxxx9

Aperson lifts a 4.5 kg cement block a vertical distance of 1.2 m and then carries the block horizontal- ly a distance of 7.3 m. determine the work done by the person and by the force of gravity in this process.

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When a person lifts the block, the block has more potential energy. Therefore the person does positive work on the block. work = m g h work = (4.5 kg) (9.80 m/s^2) (1.2 m) work = 52.92 joules The person's work on the block is 52.92 joules When the block is being raised, the force of gravity opposes the motion. Therefore the force of gravity does negative work on the block. work = - (force) (h) work = - m g h work = -(4.5 kg) (9.80 m/s^2) (1.2 m) work = -52.92 joules The work done by the force of gravity on the block is -52.92 joules Note that when the block is moved horizontally, the potential energy does not change. Therefore there is no work done on the block when it moves horizontally (we are assuming that the kinetic energy does not change).

Answer from: neariah24

The work done by the person is positive and its value is 52.92 J.

The work done by gravity is negative and its value is -52.92 J

Given data:

The mass of cement block is, m = 4.5 kg.

The vertical distance raised by the block is, $d=1.2 \;\rm m$ .

The horizontal distance covered by the block is, d' = 7.3 m.

Since, person lifts the block to assure some displacement of block. So, person will do a positive work. And work done by the person is stored in the form of potential energy of block.

Therefore,

W = mgd

$W =4.5 \times 9.8 \times 1.2 \\W =52.92 \;\rm J$

Thus, the work done by the person is 52.92 J.

And gravity will oppose the motion of block, so it will do negative work on the block. Therefore,

Work done by gravity = - (Work done by person)

Work done by gravity = - 52.92 J

Thus, the work done by gravity is -52.92 J.

Learn more about the work done here:

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Aperson lifts a 4.5 kg cement block a vertical distance of 1.2 m and then carries the block horizont...

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