Advertisements
Advertisements
Question
A boy throws a rubber ball vertically upwards. What type of work, positive or negative, is done : by the force applied by the boy?
(a) by the force applied by the boy?
(b) by the gravitational force of earth?
Advertisements
Solution
A boy throws a rubber ball vertically upwards. Work done by the two forces:
(a) Work done by the force applied by the boy is positive because the displacement of the ball is in the direction of force applied.
(b) Work done by the gravitational force is negative because the displacement of the ball is opposite to the direction of gravitational force.
APPEARS IN
RELATED QUESTIONS
A weight lifter lifted a load of 200 kgf to a height of 2.5 m in 5 s. Calculate:
- the work done, and
- the power developed by him. Take g = 10 N kg-1
A machine raises a load of 750 N through a height of 16 m in 5 s. calculate:
- energy spent by machine,
- power at which the machine works.
Explain by an example that a body may possess energy even when it is not in motion.
The work done by a force acting obliquely is given by the formula : W = F cos θ ✕ s. What will happen to the work done if angle θ between the direction of force and motion of the body is increased gradually? Will it increase, decrease or remain constant.
What is the work done against gravity when a body is moved horizontally along a frictionless surface?
Give an example
Electrical energy changes to heat energy.
A force is applied on a body of mass 20 kg moving with a velocity of 40 ms−1. The body attains a velocity of 50 ms−1 in 2 seconds. Calculate the work done by the body.
One labourer carried four pans of road metal through a distance of 100 metres. If he carries two pans of road metal through a 200 metre distance ______ work will be done.
A body of mass 0.5 kg travels on straight line path with velocity v = (3x2 + 4) m/s. The net work done by the force during its displacement from x = 0 tox = 2 m is ______.
