Q3. Compare the two different scenarios of getting a heavy piece of furniture up five steps to the main entrance door of a house.
(a) Lifting the heavy piece of furniture and carrying it up the five steps.
(b) Using a long ramp to push the heavy piece of furniture up to the main entrance door of a house.
What is the work done by gravity in either scenario? What is your work done in either scenario? Is there any other work involved?
To compare the work done by gravity and the work done by you in each scenario, we need to understand the concept of work.
Work is defined as the product of force and displacement in the direction of the force. In both scenarios, we need to consider the force applied to move the heavy furniture and the displacement it undergoes.
(a) Lifting the heavy piece of furniture and carrying it up the five steps:
In this scenario, you would apply an upward force to lift the furniture against the force of gravity. The work done by gravity is negative because it acts in the opposite direction of the displacement. Therefore, the work done by gravity is given by:
Work gravity = - (force of gravity x vertical displacement)
The work done by you in this scenario is positive because you are applying a force in the same direction as the displacement. Therefore, the work done by you is given by:
Work you = force applied x vertical displacement
(b) Using a long ramp to push the heavy piece of furniture up:
In this scenario, you would be pushing the furniture up the ramp, exerting a force parallel to the ramp's surface. This force is not directly opposed by gravity; therefore, the work done by gravity is negligible or zero.
The work done by you in this scenario is positive because you are applying a force in the same direction as the displacement. Therefore, the work done by you is given by:
Work you = force applied x horizontal displacement
In both scenarios, there may be additional work involved due to friction. Friction is the force acting against the motion of the furniture, and it might be present when lifting or pushing the furniture. The work done against friction can be calculated by multiplying the force of friction by the displacement in the direction of the force.
So, in summary:
(a) Work done by gravity: - (force of gravity x vertical displacement)
Work done by you: force applied x vertical displacement
Additional work against friction might be present.
(b) Work done by gravity: negligible/zero
Work done by you: force applied x horizontal displacement
Additional work against friction might be present.
It is worth noting that when using a ramp, the horizontal displacement is typically longer than the vertical displacement. This means that the work done by you may be less compared to lifting the furniture directly, although there may still be additional work involved due to friction.