With reference to the scientific concept of 'work', consider the following statements: 1. Work is said to be done only when a force acts on an object and the object is displaced. 2. If a person pushes a huge rock hard but it does not move, scientific work is considered to be done due to the exhaustion of energy. 3. Mental labour, such as reading or thinking, does not constitute work in science. Which of the statements given above is/are correct?

The correct option is (c) 1 and 3 only. Explanation In physics, the concept of work is strictly defined and differs from the general understanding of labour or effort. Scientific work is a scalar quantity measured as the product of the force applied to an object and the displacement of that object in the direction of the force. The mathematical expression is W = F × s (where F is force and s is displacement). Statement-wise Analysis - Statement 1 is Correct: For work to be done in a scientific sense, two essential conditions must be met: a force must be exerted on an object, and the object must undergo displacement. If either condition is absent (e.g., force is zero or displacement is zero), no work is done. - Statement 2 is Incorrect: If a person pushes a huge rock and it does not move, the displacement (s) is zero. According to the formula W = F × 0, the work done on the rock is zero. While the person may feel exhausted due to internal physiological energy expenditure (muscle contractions), this does not constitute work on the external object in terms of physics. - Statement 3 is Correct: Mental activities such as reading, thinking, or studying do not involve the application of a physical force on an object resulting in displacement. Therefore, despite the mental effort or fatigue involved, these activities do not constitute work according to scientific definitions. Key Takeaway: In science, work is done only if there is a physical displacement of an object caused by an applied force. Effort without displacement yields zero work.

With reference to the scientific concept of… - NCERT Class 9 Science MCQ

NCERT Class 9 Science — Chapter 4: Work and energy

mcqeasy

With reference to the scientific concept of 'work', consider the following statements:

Work is said to be done only when a force acts on an object and the object is displaced.
If a person pushes a huge rock hard but it does not move, scientific work is considered to be done due to the exhaustion of energy.
Mental labour, such as reading or thinking, does not constitute work in science.

Which of the statements given above is/are correct?

NCERT textbook question

From NCERT Science - class 9 · Page 114

Options

A1 and 2 only
B2 only
C1 and 3 only
D1, 2 and 3

Did you get this right?

Solution

The correct option is (c) 1 and 3 only.

Explanation

In physics, the concept of work is strictly defined and differs from the general understanding of labour or effort. Scientific work is a scalar quantity measured as the product of the force applied to an object and the displacement of that object in the direction of the force. The mathematical expression is W = F × s (where F is force and s is displacement).

Statement-wise Analysis

Statement 1 is Correct: For work to be done in a scientific sense, two essential conditions must be met: a force must be exerted on an object, and the object must undergo displacement. If either condition is absent (e.g., force is zero or displacement is zero), no work is done.
Statement 2 is Incorrect: If a person pushes a huge rock and it does not move, the displacement (s) is zero. According to the formula W = F × 0, the work done on the rock is zero. While the person may feel exhausted due to internal physiological energy expenditure (muscle contractions), this does not constitute work on the external object in terms of physics.
Statement 3 is Correct: Mental activities such as reading, thinking, or studying do not involve the application of a physical force on an object resulting in displacement. Therefore, despite the mental effort or fatigue involved, these activities do not constitute work according to scientific definitions.

Key Takeaway: In science, work is done only if there is a physical displacement of an object caused by an applied force. Effort without displacement yields zero work.

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A car and a truck are moving with the same velocity. If the truck is four times as massive as the car, how does the kinetic energy of the truck compare to that of the car?

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