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 shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative, positive or zero.
Solution and Explanation
(i)
Since in this diagram displacement is perpendicular to the direction of force, so work done is zero.
(ii)
Since in this diagram displacement is in the direction of force, so work done is positive.
(iii)
Since in this diagram displacement is in the opposite direction of the force applied hence work done is negative.
Top Questions on Work
- In an actual regenerative Rankine cycle, the net work out put will be _____ as compared to simple Ranking cycle.
- A metal has work function \(w_0\) = 3.3×10-19 J. What should be the minimum frequency of the incident radiation that can remove an electron from the metal surface? [Given h = 6.6x10-34 J-s]
- An object thrown at a certain angle to the ground moves in a curved path and falls back to the ground. The initial and the final points of the path of the object lie on the same horizontal line. What is the work done by the force of gravity on the object?
- Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
• Suma is swimming in a pond.
• A donkey is carrying a load on its back.
• A wind-mill is lifting water from a well.
• A green plant is carrying out photosynthesis.
• An engine is pulling a train.
• Food grains are getting dried in the sun.
• A sailboat is moving due to wind energy. - An object of mass, m is moving with a constant velocity, v. How much work should be done on the object in order to bring the object to rest?
Questions Asked in CBSE Class IX exam
- Match the phrases in Column A with their meanings in Column B.
A B (i) broke out (a) an attitude of kindness, a readiness to give freely (ii) in accordance with (b) was not able to tolerate (iii) a helping hand (c) began suddenly in a violent way (iv) could not stomach (d) assistance (v) generosity of spirit (e) persons with power to make decisions (vi) figures of authority (f) according to a particular rule, principle, or system - CBSE Class IX
- My childhood
ABC is a triangle in which altitudes BE and CF to sides AC and AB are equal (see Fig). Show that
(i) ∆ ABE ≅ ∆ ACF
(ii) AB = AC, i.e., ABC is an isosceles triangle.
- CBSE Class IX
- Some Properties of a Triangle
- The author speaks both of people who were very aware of the differences among them and those who tried to bridge these differences. Can you identify such people in the text?
- CBSE Class IX
- My childhood
- What did his father say to this?
- CBSE Class IX
- My childhood
- The following data on the number of girls (to the nearest ten) per thousand boys in different sections of Indian Society is given below:
Section
Number of girls per thousand boys Scheduled Caste (SC)
940
Scheduled Tribe (ST)
970
Non-SC/ST
920
Backward districts
950
Non-backward districts
920
Rural
930
Urban
910
(i) Represent the information above by a bar graph.
(ii) In the classroom discuss what conclusions can be arrived at from the graph.- CBSE Class IX
- Graphical Representation of Data
Concepts Used:
Work
Work is the product of the component of the force in the direction of the displacement and the magnitude of this displacement.
Work Formula:
W = Force × Distance
Where,
Work (W) is equal to the force (f) time the distance.
Work Equations:
W = F d Cos θ
Where,
W = Amount of work, F = Vector of force, D = Magnitude of displacement, and θ = Angle between the vector of force and vector of displacement.
Unit of Work:
The SI unit for the work is the joule (J), and it is defined as the work done by a force of 1 Newton in moving an object for a distance of one unit meter in the direction of the force.
Work formula is used to measure the amount of work done, force, or displacement in any maths or real-life problem. It is written as in Newton meter or Nm.