Do you know your Basics?- IV

Classical Mechanics Level 2

The work done in lifting a mass of 1 kg to a height of 9.8 m is?

Input your answer in Joules and in 2 decimal places.

And also take the magnitude of acceleration due to gravity as 9.8 m/s 2 9.8 \text{ m/s}^2 .


The answer is 96.04.

Swapnil Das by Swapnil Das , 20, India

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5 solutions

Sarthak Rath
May 13, 2015

we apply a force of

( m x g ) when we lift the box up.

so that is equal to 1kg x 9.8 m s − 2 ms^{-2} = 9.8 N

we know work done is equal to force x displacement

hence, 9.8N x 9.8m = ( 9.8 ) 2 (9.8)^2 J = 96.04 J \boxed{96.04 J}

4 Helpful 0 Interesting 0 Brilliant 0 Confused

Dude.. In this situation of lifting a box up we are applying force in upward direction and acc. due to gravity is acting in downward direction. Also acc. Is in upward direction so how can u put a=g in F=ma Since, we read this formula as... Net Force acting on a body is equal to the product of mass of that body and acceleration produced in the DIRECTION OF FORCE

Gaurav Jangra - 5 years, 10 months ago

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since direction isn't specified..... no clue of it! so if we take the direction towards earth as positive, then acc. is positive and 9.8 and towards the earth i can't get it where ur problem is like why can't a=g be true?? in this case, acc. is g!! no offence :)

Sarthak Rath - 5 years, 9 months ago

To cancel out the acceleration due to gravity we have to apply an upward acceleration more or equal to the acceleration of gravity.

Cody Estes - 5 years ago

work done = m.g.h

=1 X 9.8 X 9.8

=96.04

1 Helpful 0 Interesting 0 Brilliant 0 Confused

Did the same thing...

Hon Ming Rou - 5 years, 11 months ago
Rama Devi
May 14, 2015

We know that work done is equal to the product of mass,acceleration due to gravity and height.By substituting the values of the given parameters,we the the answer as 96.04 joule

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Krishna Karthik
Nov 19, 2018

W= F d Fd

W = m g ∗ h W=mg*h = 9. 8 2 9.8^2 =96.04J

0 Helpful 0 Interesting 0 Brilliant 0 Confused
An Dar
May 18, 2015

Force= m x a
Force=1 x 9.8=9.8
W=Force x Displacement
W=9.8 x 9.8=96.04 Nm( Joule)


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