Advertisements
Advertisements
Question
What are the quantities on which the amount of work done depends? How are they related to work?
Solution
The work done by a force on a body depends on two factors:
(i) Magnitude of force applied
(ii) Displacement in the direction of force applied
The relation between work (W), force (F) and displacement (S) is given by following equation:
W = F.S. cos θ
Where,
(W) - Work done
(F) - Force
(S) - Displacement
(θ) - Angle between the force applied and displacement of the body.
APPEARS IN
RELATED QUESTIONS
In each of the following a force, F is acting on an object of mass, m. The direction of displacement is from west to east, as shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative, positive or zero.
State the S.I. unit of work and define it.
A force of 30 N acts on a body and moves it through a distance of 5 m in the direction of force. Calculate the work done by the force.
A man lifts a mass of 20 kg to a height of 2.5 m. Assuming that the force of gravity on 1 kg mass is 10 N, find the work done by the man.
A car is running at a speed of 15 km h-1 while another similar car is moving at a speed of 45 km h-1. Find the ratio of their kinetic energies.
Fill in the blank with suitable word :
Work is measured as a product of __________ and __________
Choose one or more correct alternatives.
Joule is the unit of ______.
- force
- work
- power
- energy
A weight lifted a load of 200 kgf to a height of 2.5 m in 5 s. calculate: (i) the work done, and (ii) 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 5s. calculate:
(i) work done by machine,
(ii) power at which the machine works.
What do you understand by 'potential energy' and 'Kinetic energy'? Give three examples of each to illustrate your answer.
A canon ball of mass 500g is fired with a speed of 15m/s-1. Find: its momentum.
How much energy is gained by a box of mass 20 kg when a man, runs carrying the box with a speed of 3 m/s-1 to catch the bus?
A coolie, with a load of 30 kg on his head, walks on the platform. If he walks a distance of 60 m, what is the work done by him?
What do you understand by the term energy? Is energy a scalar or vector? How is the energy possessed by a body measured?
Name two places in India where electricity is generated from nuclear power plants.
A truck driver can load oil drums into the back of the truck by pushing them up a sloping plank, or by lifting them directly. Each drum has a mass of 80 kg, the plank is 3 m long, and the back of the truck is 0.8 m above the ground.
(i) How much force would be needed to lift a drum into the truck directly/without using the plank? (Take g = 10 m/s2)
(ii) How much energy would be required in lifting the drum into the truck without the plank?
(iii) If the force needed to push the drum up the plank is 300 N, why is this less than the answer to part (i)?
(iv) When the truck is loaded, the driver drives off. List the major energy changes that take place in moving the truck.
(v) The driver has to stop at the factory gates. What happens to the kinetic energy of the truck?
Look at the activity below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
A wind-mill is lifting water from a well.
