## Force And Laws Of Motion Class 9

If you are looking for Force And Laws Of Motion Class 9 Notes and MCQ the your search ends here. we are providing the same for students to prepare for their exams.

**Velocity and Speed:**

Velocity refers to the displacement that occurs in unit time.

Speed refers to the distance traveled in unit time.

In SI units, velocity is measured in m/s, while in CGS units, it’s measured in cm/s.

**Difference Between Speed and Velocity:**

Speed is related to distance, while velocity is related to displacement.

Speed and velocity share the same units but have distinct meanings.

**Uniform and Non-Uniform Motion:**

Uniform motion involves equal displacements in equal time intervals.

Non-uniform motion refers to unequal distances covered in equal time intervals.

**Circular Motion:**

Uniform circular motion occurs when an object moves with constant speed along a circular path.

Change in velocity in this case is due to a change in direction.

**Acceleration:**

Objects can have positive or negative acceleration.

Positive acceleration corresponds to velocity increase, negative acceleration to velocity decrease.

Zero acceleration means constant velocity.

**Momentum:**

Momentum is the product of mass and velocity: P=mÃ—vP=mÃ—v.

Momentum is a vector quantity with magnitude and direction.

The rate of change of momentum is proportional to the applied force.

**Newton’s Laws:**

Force depends on both mass and velocity of an object.

The SI unit of force is the newton (N), while in CGS, it’s the dyne.

Newton’s second law: F=maF=ma, where FF is force, mm is mass, and aa is acceleration.

**Important Values:**

Speed of sound in dry air: 343.2 m/s

Speed of light: 3Ã—1083Ã—108 m/s

Earth’s speed of revolution around the sun: 29770 m/s

Force and Laws of motion class 9 MCQ

Question 1: What is velocity?

a) The distance traveled by an object in unit time.

b) The rate of change of distance with time.

c) The displacement that occurs in unit time.

d) The time taken to cover a unit distance.

Answer: c) The displacement that occurs in unit time.

Question 2: What is the SI unit of velocity?

a) m/sÂ²

b) cm/s

c) kg m/s

d) m/s

Answer: d) m/s

Question 3: Which scientist first measured speed as distance divided by time?

a) Isaac Newton

b) Albert Einstein

c) Galileo Galilei

d) Johannes Kepler

Answer: c) Galileo Galilei