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10 Questions MCQ Test Science Class 9 - Test: Work and Energy- Assertion & Reason Type Questions- 1

Test: Work and Energy- Assertion & Reason Type Questions- 1 for Class 9 2023 is part of Science Class 9 preparation. The Test: Work and Energy- Assertion & Reason Type Questions- 1 questions and answers have been prepared according to the Class 9 exam syllabus.The Test: Work and Energy- Assertion & Reason Type Questions- 1 MCQs are made for Class 9 2023 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Work and Energy- Assertion & Reason Type Questions- 1 below.
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Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 1

Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Work done is different while climbing on stairs or using lift.

Reason : Work done depends only on the initial and final position of the object.

Detailed Solution for Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 1
Work done is a state function. It depends on the initial and final position of the object and not on the path followed. In the above example initial and final position is same therefore work done is same in both cases.
Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 2

Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Work done by the force can be positive or negative.

Reason : Force is taken as positive when it acts opposite to the direction of displacement.

Detailed Solution for Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 2

Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Work done by a force is given by the equation: W = F * d * cos(θ), where F is the force, d is the displacement, and θ is the angle between the force and displacement vectors. The angle between the force and displacement vectors is measured in radians. The cosine of the angle is positive when the force and displacement vectors are in the same direction, and negative when they are in opposite directions. The work done by the force can be positive or negative depending on the direction of the force and displacement. If the force and displacement are in the same direction, the work done is positive and if they are in opposite direction, the work done is negative. The reason given in the statement that force is taken as positive when it acts opposite to the direction of displacement, supports the assertion that work done by the force can be positive or negative.

Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 3

Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : A 40 kg girl is running along a circular path of radius 1 m with a uniform speed. The work done by the girl is zero.

Reason : In this case, displacement is zero after one complete rotation.

Detailed Solution for Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 3

Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

The work done by a force on an object is given by the equation W = F * d * cos(θ), where F is the force, d is the displacement and θ is the angle between the force and displacement vectors. In this case, the girl is running along a circular path with a uniform speed. The force acting on her is the force of gravity, which is always perpendicular to the surface of the earth. The angle between the force and displacement vectors is 90 degrees, so cos(90) = 0.

Since the angle between the force and displacement vectors is 90 degrees, the work done by the force of gravity on the girl is zero. Additionally, the reason given in the statement that displacement is zero after one complete rotation, also supports the assertion that the work done by the girl is zero.

 

Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 4

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Energy possessed by a rolling stone is kinetic energy.

Reason : Kinetic energy possessed by an object is due to its motion.

Detailed Solution for Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 4
Kinetic energy is the energy possessed by an object due to its motion. Moving objects possess kinetic energy. For example, energy possessed by a rolling stone is kinetic energy.
Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 5

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion: The potential energy of a free falling object decreases progressively.

Reason: It violates the law of conservation of energy.

Detailed Solution for Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 5
No, it does not violate the law of conservation of energy. Potential energy is converted into total mechanical energy and hence, it remains conserved.
Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 6

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion: Unit of energy is same as that of work.

Reason: The commercial unit of energy is Joule.

Detailed Solution for Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 6
The unit of energy is same as that of work that is Joule. Joule is the S.I unit of energy but it is a smaller unit. For commercial purpose, we use kWh as the unit of energy. 1 kWh = 3.6 × 106 joules.
Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 7

Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion: A lamp consumes 1000 J of electrical energy in 10 s. Its power is 100 W.

Reason: Power is obtained by dividing the energy consumed by the time taken.

Detailed Solution for Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 7
Power of lamp = Energy/ Time

P = 1000/10 = 100W

Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 8

Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion: The physical quantity defined by rate of doing work is Energy.

Reason: Its SI unit is J/s.

Detailed Solution for Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 8
The physical quantity defined by rate of doing work is power. Its SI unit is J/s or Watt.
Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 9

Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion: SI unit of power is Joules.

Reason: One kWh is equal to 3.6 × 106 J.

Detailed Solution for Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 9

SI unit of power is Watt. One kWh is equal to 3.6 ×106 J.

Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 10

Direction: In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as:

Assertion : A crane P lifts a car up to a certain height in 1 min. Another crane Q lifts the same car up to the same height in 2 min. Then crane P consumes two times more fuel than crane Q.

Reason : Crane P supplies two times more power than crane Q.

Detailed Solution for Test: Work and Energy- Assertion & Reason Type Questions- 1 - Question 10
Fuel is actually the power supplied by a mechanical machine when there is conversion of heat energy to mechanical energy. Here, the fuel consumed by the cranes is equal to the power supplied by the cranes.Let the mass of the car be m, g be the acceleration due to gravity and h be the height up to which the car is lifted by the cranes.

For crane P: The work done by the crane P is equal to WP = mgh. The power supplied by the crane will be PP = WP/t = mgh/1 = mgh and the fuel consumed will also be the same.

For crane Q: The work done by the crane Q is equal to WQ = mgh. The power supplied by the crane will be PQ = WQ/t = mgh/2 and the fuel consumed will also be the same.

As you can see that PQ = PP/2 → PP = 2PQ, which means that the crane P consumes two times more fuel than crane Q and also crane P supplies two times more power than crane Q.

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