# Class 9 physics chapter 2 force and laws of motion question answer

class 9 physics chapter 2 force and laws of motion question answer

class 9 physics chapter 2 force and laws of motion question answer

Q1. What name is given to the product of the mass and velocity of a body?

Answer: The product of the mass and velocity of a body is known as “momentum.” Mathematically, momentum (p) is defined as:

Momentum (p) = mass × velocity

In symbols, it’s often represented as:

p = m × v

Where:

• “p” represents momentum.
• “m” represents the mass of the body.
• “v” represents the velocity of the body.

Momentum is a vector quantity, meaning it has both magnitude and direction. It’s a fundamental concept in physics and is used to describe the motion and interaction of objects in various contexts.

Q2. Name the physical quantity which is considered to be a measure of the quantity of motion of a body.

Answer: The physical quantity that is considered to be a measure of the quantity of motion of a body is “momentum.” Momentum is a property of an object that accounts for both its mass and its velocity. It quantifies the amount of motion an object possesses and how difficult it is to stop or change the motion of that object.

In mathematical terms, momentum (p) is the product of the mass (m) of an object and its velocity (v):

Momentum (p) = mass × velocity

p = m × v

Momentum is an essential concept in physics and plays a crucial role in describing the behavior of objects in motion, as well as in interactions between objects.

Q3. What is the SI unit of momentum?

Answer: The SI (International System of Units) unit of momentum is kilogram-meter per second (kg·m/s). This unit is a combination of the SI unit for mass (kilogram) and the SI unit for velocity (meter per second). The momentum of an object is typically expressed in kilogram-meter per second or its multiples, such as newton-seconds (N·s), which is equivalent to kilogram-meter per second.

Q4. State whether momentum is scalar or vector.

Answer: Momentum is a vector quantity. This means that it has both magnitude and direction. In physics, a vector quantity is described not only by its numerical value (magnitude) but also by its direction in space. In the case of momentum, both the mass and velocity of an object contribute to its momentum, and both of these factors have directions associated with them. Therefore, momentum must be considered as a vector quantity.

Q5. What is the total momentum of the bullet and the gun before firing?
Q6. Name the physical quantity whose unit is kg.m/s.
Q7. What will be the momentum of a body of mass ‘m’, which is moving with the velocity V?
Q8. What is the usual name of the forces which cannot produce motion in a body but only change its shape?

Q5. The total momentum of the bullet and the gun before firing is zero.

Q6. The physical quantity whose unit is kg·m/s is momentum.

Q7. The momentum of a body of mass ‘m’ moving with the velocity ‘V’ is given by the formula: Momentum = mass × velocity. In symbols, it’s often represented as: p = m × V.

Q8. The usual name of the forces that cannot produce motion in a body but only change its shape is “non-conservative” or “internal” forces. These forces typically don’t contribute to changes in the total mechanical energy of a system but can cause deformations or changes in the shape of an object. Examples of such forces include tension, compression, and shear forces.