Advertisements
Advertisements
Question
For the following scenario, state whether the work done by gravity is positive, negative, or zero.
A car in neutral gear is coming down the slope.
Advertisements
Solution
Positive work is done.
Explanation:
When a car in neutral gear is coming down the slope, the direction of displacement covered by it is parallel to the direction of force of gravity (downwards), so the work done on the car by the force of gravity is positive.
RELATED QUESTIONS
A satellite revolves around the earth in a circular orbit. What is the work done by the force of gravity? Give reason.
The work done by a fielder when he takes a catch in a cricket match, is negative. Explain.
State two factors on which power spent by a source depends. Explain your answer with examples.
Is it possible that no transfer of energy may take place even when a force is applied to a body?
A pump is used to lift 600 kg of water from a depth of 75 m in 10s. Calculate:
- The work done by the pump,
- the power at which the pump works, and
- The power rating of the pump if its efficiency is 40%. (Take g = 10m s-2).
`["Hint" : "Efficiency" = "useful power"/"power input"]`
A man raises a box of mass 50 kg to a height of 2 m in 20s, while another man raises the same box to the same height in 50s. Calculated:
- the work done, and
- the power developed by each man. Take g = 10 N kg-1.
A machine raises a load of 750 N through a height of 16 m in 5 seconds. Calculate the power at which the machine works.
A coolie carries a load of 30 kgf through a distance of 500 m in 5 minutes while another coolie B carries the same load through the same distance in 10 minutes. Compare the
(i) work done, and
(ii) power developed. (Take: g = 10md−2)
