### What is thermometry?

Thermometry The branch of heat relating to the measurement of the temperature of a body is called thermometry. The thermometer is an instrument used to measure the temperature of a body. The essential requisites of a thermometer are given as under:  1) Construction, 2) Calibration, and 3) Sensitiveness. For the construction of a thermometer, the proper choice of a substance, whose physical property varies uniformly with rising in temperature, is essential. 1) Construction The physical property of a substance plays an important role in the construction of a thermometer. In a mercury thermometer, the principle of expansion of mercury with rising temperature is used. The platinum resistance thermometer is based on the principle of the change in resistance with a change in temperature. The gas thermometer is based on the principle of change in volume or pressure with a change in temperature. 2) Calibration  When a thermometer is constructed, it should be properly calibrated. The standa

## 👉All Chapter Contents👈

• 3.1 Inertia of Concept of Force - Newton's First Law
• 3.2 Nature of Fundamental Forces
• 3.3 Balanced and Unbalanced Forces
• 3.4 Momentum
• 3.5 Collision
• 3.6 Effect of Force on Motion: Newton's Second Law
• 3.7 Gravitational Force
• 3.8 Newton's Third Law
• 3.9 Frictional Force

## Question Bank

• State Newton's first law.
• Explain why we never observe that a body in motion keeps its perpetual motion forever?
• What does inertia mean?
• What is inertia of rest?
• What is inertia of motion?
• Mass is the measurement of inertia? Explain.
• What is force?
• What is contact force?
• What is a non-contact force?
• Explain that the concept of inertia is found from Newton's first law.
• Which way does passenger lean when the moving bus suddenly breaks and why?

• What is fundamental force?
• How many fundamental forces in nature and what are they?
• What do you mean by gravity?
• What do you mean by electromagnetic force?
• What do you mean by weak nuclear force?
• What do you mean by strong nuclear force?
• Discuss the comparative intensity of the fundamental forces.

## 3.3 Balanced and Unbalanced Forces

• What do you mean by balanced force?
• What do you mean by unbalanced force?

• What is momentum?
• Determine the unit and dimension of momentum.
• What do you understand by momentum 200 kgm/s?
• Write the law of conservation of momentum.

## 3.5 Collision

• Write the law of conservation of momentum?
• Prove the law of conservation of momentum.
• Write the law of conservation of energy?
• Show that before the collision and after the collision total momentum is equal.
• Explain the necessity of force and motion in the case of safe journey.

• Write the second law of Newton.
• Prove that, F = ma.
• Write the unit and dimension of force.

## 3.7 Gravitational Force

• What is gravitational force?
• What is the value of the gravitational constant 'G'?

• Write Newton's third law.
• Explain Newton's third law.

## 3.9 Frictional Force

• What is friction?
• What is frictional force?
• Explain the origin of friction.
• How many types of friction and what are they?
• What is static friction?
• What is sliding friction?
• What is rolling friction?
• What is fluid friction?
• Explain the effect of friction on the motion?
• Why there is a groove on the surface of the car tire?
• Explain how friction can be reduced?
• Explain how friction can be increased?
• Explain why friction is a necessary evil?

# Secondary Physics

## Mathematical Problems

• What is the force to be applied to a mass of 50 kg to produce an acceleration of 4 ms-2? [Ans: 200 N]

• A boy pushes a box of mass 20 kg with a force of 50 N. What will be the acceleration of the box? [Ans: 2.5 ms-2]

• A force of 2000 N acts on a body of mass 20 kg for a time of 0.1 s. What is the change of momentum of the body? [Ans: 200 kgms-1]

• A bullet of mass 10 g was shot from a gun with a velocity of 500 ms-1. If the mass of the gun is 2 kg, find the backward velocity of the gun. [Ans: 2.5 ms-1]