Access Answers of Science NCERT Class 9 Chapter 11: Work and Energy (All intext and exercise questions solved)
Exercise-11.1 Page: 148
1. A force of 7 N acts on an object. The displacement is, say 8 m, in the direction of the force. Let us take it that the force acts on the object through the displacement. What is the work done in this case?
When a force F acts on an object to move it in its direction through a distance S, the work is done
The work on the body is done by force
Work done = Force × Displacement
W = F × S
F = 7 N S = 8 m
So, work done,
W = 7 × 8
W = 56 Nm
W = 56 J
Exercise-11.2 Page: 149
1. When do we say that work is done?
Work is completed whenever the given conditions are satisfied:
(i) A force acts on the body.
(ii) There’s a displacement of the body caused by the applied force on the direction of the applied force.
2. Write an expression for the work done when a force is acting on an object in the direction of its displacement.
When a force F displaces a body through a distance S within the direction of the applied force, then the work done W on the body is given by the expression:
W = F × S
3. Define 1 J of work.
1 J is that the quantity of labor done by a force of one N on associate degree object that displaces it through a distance of one m within the direction of the applied force.
4. A pair of bullocks exerts a force of 140 N on a plough. The field being ploughed is 15 m long.
How much work is done in ploughing the length of the field?
Work done by the bullocks is given by the expression:
W= F × d
Applied force, F = 140 N
Displacement, d = 15 m
W= a hundred and forty × fifteen = 2100 J
Hence, 2100 J of labour is finished in tilling the length of the sector.
Er. Aman Blogger, Educator