Advertisements
Advertisements
Question
For the following scenario, state whether the work done by gravity is positive, negative, or zero.
A person climbs a ladder.
Advertisements
Solution
Negative work is done.
Explanation:
When a person climbs a ladder (upward), the displacement covered by the person is opposite to the direction of the force of gravity (downward), so the work done on the person by the force of gravity is negative.
RELATED QUESTIONS
Give the expression for mechanical advantage of an inclined plane in terms of the length of an inclined plane.
Draw a simplified diagram of a lemon crusher, indicting of load and effort
A satellite revolves around the earth in a circular orbit. What is the work done by the force of gravity? Give reason.
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"]`
It takes 20 s for a person A of mass 50 kg to climb up the stairs, while another person B of same mass does the same in 15 s. Compare the power developed by the persons A and B.
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.
What do you understand by work? Is work a scalar or a vector quantity?
Justify the statement. “Power can be expressed as the product of force and velocity.”
Calculate the work done when:
A car is moved on a rough road through 30 m against a frictional resistance of 75 N.
