A boy of mass $40 k g$ runs upstairs and reaches the roof at height $8 m$ in $5 s$ . $($ Take $g = 10 m s^{- 2})$ . Calculate the work done by him against gravity.

400 J

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3200 J

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320 J

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200 J

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Solution

The correct option is B $3200 J$
$F o r c e = m \times a$ .Given mass is equal to $40 K g$ and as we are finding force of gravity $a = g$ .

Hence $F = 40 \times 10 = 400 N$ .Here given that displacement is 8. $W o r k = F \times S \times cos θ$ .

Here $F = 400 N, S = 8 m$ and angle is 180 degree where $c o s 180^{o} = - 1$ .

Hence $W = 400 \times 8 = 3200 J o u l e$ .The obtained value is against the gravity.

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Similar questions

40 k g

8 m

5 s

(

g = 10 m s^{- 2})

40 k g

8 m

5 s

(

g = 10 m s^{- 2})

A boy of mass 40kg climbs up the stairs and reaches the roof at a height 8m in 5s.Calculate :

1-the force of gravity acting on the boy

2-the work done by him against the gravity

3-the power sent by the boy

(take g=10m 1/s²)

g = 10 m s^{-} 2.

(g = 10 m / s^{2})

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