Energy and Work Class-8th Goyal Brothers Physics Solutions Chapter-4 (Energy), unit-1 (Energy and Work). We Provide Step by Step Answers of Objective, True False, Incorrect and Correct, Fill in the blanks, Match the following , Short/Long Answer Type of Chapter-4 (Energy), unit-1 (Energy and Work) Visit official Website CISCE for detail information about ICSE Board Class-8.
Energy And Work ICSE Class-8th Goyal Brothers Physics Solution Chapter-4 Unit-1
| Board | ICSE |
| Class | 8th |
| Subject | Physics |
| Book Name | Goyal Brothers |
| Chapter-4 | Energy |
| Unit-1 | Energy and Work |
| Topic | Solution of exercise questions |
| Session | 2023-24 |
OBJECTIVE QUESTION
Energy And Work ICSE Class-8th Goyal Brothers Physics Solution Chapter-4 Unit-1
Que: A. Fill in the blank spaces by choosing the correct words from the list given below :
List : direction, joule, work, energy, force
1. Ability to do work is called energy.
2. When a force causes displacement in its own direction, work is said to be done.
3. An elephant uprooting a small tree does work.
4. The work done by a body is the product of force and displacement.
5. Joule is the SI unit of work.
Que: B. Write ‘True’ or ‘False’ for the following statements :
| Statement | True/False |
| 1. SI unit of work or energy is joule. | T |
| 2. The product of force and the displacement caused by it is called pressure. | F |
| 3. A student preparing his lessons for monthly test does hard work. | T |
| 4. A boy carrying a school bag on his shoulder does no work. | T |
| 5. The more the force is applied on a body to cause displacement, the more is the work done. | F |
Que: C. Statements given below are incorrect. Write the correct statements :
Question: 1. Work is done when we hold a pile of books on our hands.
Answer: Work is not done when we hold a pile of books on our hands.
Question: 2. Work done by a body is the product of pressure and displacement.
Answer: Work done by a body is the product of force and displacement.
Question: 3. Work is done when a force causes displacement at right angles to its own direction.
Answer: Work is done when a force causes displacement at not right angles to its own direction.
Question: 4. A headmaster giving a speech in a school assembly does work.
Answer: A headmaster giving a speech in a school assembly mental work.
Question: 5. The SI unit of work or energy is pascal (pa).
Answer: The SI unit of work or energy is joule.
Que: D. Tick (√) the most appropriate answer :
1. The capacity to do work is called :
(a) acceleration
(b) speed
(c) energy
(d) pressure
Answer: option (c) energy is correct.
2. The work done by a body is the product of force and :
(a) distance
(b) speed
(c) displacement
(d) velocity
Answer: option (c) displacement is correct.
3. The SI unit of work is :
(a) newton
(b) pascal
(c) joule
(d) newton-meter
Answer: option (c) joule is correct.
4. 30 Joules work is done, when a force ‘F’ causes a displacement of 5 m. The magnitude of force is :
(a) 6 pascal
(b) 6 newton
(c) 6 newton-meter
(d) none of these
Answer: option (b) 6 newton is correct.
5. When is the work done in the following situation :
(i) A boy pushing a wall
(ii) A girl carrying a school bag on her shoulders
(iii) A stone falling freely
(iv) A boy climbing up the stairs
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iv)
(d) (iii) and (iv)
Answer: option (d) (iii) and (iv) is correct.
Que: E. Match the statements in Column A, with those in Column B :
| Column A | Column B |
| 1. The term used when a force causes displacement in a body in its own direction. | (a) No work done |
| 2. The ability to do work. | (b) Joule |
| 3. SI unit of work or energy. | (c) Energy |
| 4. Displacement caused by a force at right angles to its own direction. | (d) Work |
Answer:
| Column A | Column B |
| 1. The term used when a force causes displacement in a body in its own direction. | (a) Work |
| 2. The ability to do work. | (b) Energy |
| 3. SI unit of work or energy. | (c) Joule |
| 4. Displacement caused by a force at right angles to its own direction. | (d) No work done |
STUDY QUESTION
Energy And Work ICSE Class-8th Goyal Brothers Physics Solution Chapter-4 Unit-1
Question: 1. (a) What is energy?
Answer: Ability to do work, which is the ability to exert a force causing displacement of an object.
(b) What do you understand by the term work?
Answer: Work is said to be done only when the force applied to a body causes a change in the position of an object. Take an example as the objects, the car, the heavy box, and the football change their position when force is applied to them.
(c) Is the energy spent on thinking or talking a kind of work? Give reason for your answer.
Answer: In everyday language, any physical or mental activity may not be regarded as work. For example, When we talk or think our brain is working meant our brain is doing mental work but there is no displacement in this process. Then we can say, there is no energy spent on thinking or talking.
Question: 2. (a) When does a force do work?
Answer: If there is displacement due to force, than we say that work is done.
(b) State two examples when a force acting on a body does not do any work.
Answer: (i) When a person push a wall.
(ii) Tug of war, equal force on both sides.
(c) State the mathematical expression of work.
Answer: W = f . d.
(d) Name the SI unit of work.
Answer: SI unit of work is “Joules”.
Question: 3. The SI unit of work or energy is joule. Explain why the work and energy have same SI unit.
Answer: In other words, energy is the form of work that is stored and work is the one that is used. Therefore, work and energy, while not synonyms, are consistent with respect to the object. So they both have the same SI unit.
Question: 4. A force of 25 N causes a displacement of 4 m in its own direction. What is the magnitude of work done?
Answer: Solution:–
Force (F) = 25N
Displacement (S) = 4m
Work done (W) = F × S
= 25N × 4m
W= 100 J
Question: 5. A boy does a work of 800 J is dragging a sack of rice through a distance of 10 m. What is the magnitude of force applied by the boy?
Answer: Solution:–
Work done (W) = 800J
Displacement (S) = 10m
Work done (W) = F × S
800 = F × 10m
F = 80N
Question: 6. A girl applies a force of 50 N, in pushing a table such that work done by her is 25 J. Calculate the displacement produced in the table.
Answer: Solution:–
Force (F) = 50N
Work done (W) = 25J
Work done (W) = Fx
25 = 50x
x = 25/50
x = 0.5 m
— : end of Energy And Work ICSE Class-8th Goyal Brothers Physics Solution Chapter-4 Unit-1 :–-
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