This post has Class 9 Physics Chapter 6 Notes of students. Here you can find 9th Class Physics Chapter 6 MCQs. Name of this Chapter is Work and Energy. These Multiple Choice Questions are for practice to those students who are looking for it online
Work and Energy: 9th Class Physics Chapter 6 MCQs for Students 1. The work by which transfer of heat takes place are:
(A) 45°
(B) 60°
(C) 90°
(D) 180°
2. The work done in lifting a brick of mass 2 kg through the height of 5mm above the ground will be:
(A) 2.5 J
(B) 10 J
(C) 50 J
(D) 100 J
3. Which one of the following device converts light energy into electrical energy:
Electric bulb
(B) Electric generator
(C) Photo-cell
(D) Electric cell
4. The kinetic energy of a body of mass 2 kg is 25 J. Its speed is:
(A) 5 ms-¹
(B) 125 ms-¹
(C) 25 ms-¹
(D) 500 ms-¹
5. In Einstein’s mass-energy equation, C is the:
(A) Speed of sound
(B) Speed of light
(C) Speed of earth
(D) Speed of electron
6. 10-joule work is done by machine in 5 seconds. Its power will be:
(A) 2 W
(B) 10 W
(C) 25 W
(D) 502 W
7. The rate of doing work is called:
(A) Energy
(B) Torque
(C) Power
(D) Momentum
8. Energy stored in a dam’s water is:
(A) Potential energy
(B) Kinetic energy
(C) Thermal energy
(D) Electrical energy
9.If the direction of motion of the force is perpendicular to the direction of motion of the body, then work done will be:
(A) Maximum
(B) Minimum
(C) Zero
(D) None of the above
10. When a body is lifted through a height h, the work done on it appears in the form of its:
(A) Kinetic energy
(B) Potential energy
(C) Elastic potential energy
(D) Geothermal energy
This post contains Physics Chapter 6 Notes Class 9 Numericals and Short Questions for the students. Name of this Chapter is “Work and Energy”. Hereunder you will find some solved Numericals and Short Questions with Answers
Work and Energy: Physics Chapter 6 Notes Class 9 Numericals and Short Questions
Q.1: Why fossil fuels are called the non-renewable form of energy?
Ans. The fossils fuels are one used to get energy and consumed completely. So there are not renewable.
Q.2: A stone of mass 500g strikes the ground with a velocity of 20 mS-¹. How much is the kinetic energy of the stone at the time it strikes the ground?
Ans.
m = 500 g = 0.5 kg
v = 20 ms-¹
Since K.E = 1/2 mv²
K.E = 1/2 x 0.5 kg x (20 ms-¹)²
= 1/2 x 0.5 kg x 400 m² s-²
= 100 J
Q.3: Explain mass-energy equation.
Ans. Equation: E = m c²
Here E is energy, m is mass of the object while c is the speed of light (3 x 10⁸ m/s)
Q.4: Write the names of any four forms of energy.
Ans.
(i) Mechanical Energy
(ii) Heat Energy
(iii) Electrical Energy
(iv) Sound Energy
Q.5: Define potential energy and write its equation also.
Ans. The energy possessed by a body due to its position is known as its potential energy.
Equation: P.E = mg h
Q.6: What is the unit of work, define it?
Ans. SI unit of work is joule (J).
Q.7: Define kinetic energy also write its equation.
Ans. The energy possessed by a body due to its motion is called its kinetic energy.
Equation: K.E = 1/2 mv²
Q.8: Define Efficiency.
Ans. The efficiency of a system is the ratio of the required form of energy obtained from a system as output to the total energy given to it as input.
Q.9: What is the SI unit of Power? Define it.
Ans. SI unit of power is watt (W). The power of a body is one watt if it does work at the rate of 1 joule per second ( 1 Js-¹).
Q.10: Write down the equation of Einstein and the value of C.
Ans. Einstein predicted the inter-conversion of matter and energy E = mc². The value of c is the speed of light (3 x 10⁸ ms-¹⁰)
Q.11: Differentiate between sound energy and mechanical energy.
Ans.
Sound Energy: When you knock at the door, you produce sound. A sound is a form of energy. It is produced when a body vibrates.
Mechanical Energy: The energy possessed by a body both due to its motion or position is called mechanical energy.
Q.12: Define work and write its unit.
Ans. Work is done when a force acting on a body displaces it in the direction of a force.
Unit: The unit of work is Joul (J)
Q.13: Who predicted the mass-energy equation? Also, write its equation.
Ans. The relation between mass m and energy E is given by Einstein’s mass-energy equation.
Equation: E = m c²
Q.14: Define the power and write its unit.
Ans. Power is defined as the rate of doing work.
Unit: Unit of power is watt (W).
Q.15: When does a force work?
Ans. When the force acting on a body displaces it. Then work is said to be done.
Q.16: Differentiate between electrical energy and light energy.
Ans.
Electrical Energy: Electricity is one of the widely used forms of energy. We use electrical energy from batteries etc.
Light Energy: Light is an important form of energy. Most of the light comes from the sun.
Q.17: The kinetic energy of a body of mass 2 kg is 25 J. Find its speed.
Ans.
K.E = 25 J
m = 2 Kg
Formula K.E = 1/2 mV²
25 J = 1/2 (2 Kg) V²
25 = V²
V = 5 mS-¹
Q.18: Write two uses of wind energy.
Ans.
(i) Wind power is used to turn wind turbines.
(ii) In the United States, some wind farms generate more than 1300 MW of electricity a day.
Q.19: What will be the torque If a force of 150 N is applied on a spanner of 10cm?
Ans.
τ = F x L
τ = 100 x 0.1
τ = 10 Nm
