Laws of Motion Science - Laws of Motion

In CGS system, the unit of force is …………….. .

When a bullet is fired from the gun, the gun moves in backward direction. This motion is called as …………….. .

…………….. is always conserved in a collision.

S.I. unit of momentum is

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

Newton’s 1st law, Newton’s 2nd law, Newton’s 3rd law, Kepler’s laws of motion

Speed, Power, Energy, Acceleration

Displacement, Force, Momentum, Mass

Balanced force : Body at rest :: Force equation : Mass x acceleration

Inertia : Newton’s 1st law :: Rate of change of momentum : Newton’s 2nd law

Uniform circular motion: Displacement is zero :: Uniform velocity : Acceleration is zero

When body comes to rest at the end of the motion : Final velocity is zero :: When body is at rest at the starting of motion : Initial velocity is zero

Displacement : Vector quantity :: Distance : Scalar quantity

The inertia of a body is measured in terms of its mass.

In circular motion, direction of motion is tangential.

If a single force is acting on an object, it will always accelerate.

If a bus in motion is suddenly stopped, the passengers fall backwards.

A train pulling out from a station is in uniform motion.

Give formula : velocity of an object moving with uniform circular motion =

Give formula : Displacement (s) =

Give formula : Final velocity (v) =

Give formula : Force =

CGS unit of momentum

S. I. unit of acceleration

The motion in which the object covers equal distance in equal intervals of time.

What is the backward motion of the gun called?

Motion of an object along a circular path with uniform speed.

A bullet having a mass of 10 g and moving with a speed of 1.5 m/s, penetrates a thick wooden plank of mass 90 g. The plank was initially at rest. The bullet gets embedded in the plank and both move together. Determine their velocity. (Ans: 0.15 m/s)

An object moves 18 m in the first 3 s, 22 m in the next 3 s and 14 m in the last 3 s. What is its average speed? (Ans: 6 m/s)

Take 5 examples from your surroundings and give an explanation based on Newton’s laws of motion.

Balanced force and Unbalanced force

Speed and velocity.

Balanced force and Unbalanced force

Scalar quantity and Vector quantity

Positive acceleration and Negative acceleration

Newton’s laws and conservation of momentum.

Types of motion.

Moving Objects.

Newton’s laws

Types of force and their effects

Question 1. What will be the effect on the velocity of the motorcycle if its speed increases or decreases, but its direction remains unchanged?
Question 2. In case of a turning on the road, will the velocity and speed be same?
Question 3. If, on a turning, we change the direction as well as the speed of the motorcycle, what will be the effect on its velocity?

Observe the following figures. If you increase the number of sides of the polygon and make it infinite, how many times will you have to change the direction? What will be the shape of the path?

Question 1 - Measure the distance between points A and B in different ways as shown in figure
Question 2 - Now measure the distance along the dotted line. Which distance is correct according to you and why?

The mass of a cannon is 500 kg and it recoils with a speed of 0.25 m/s. What is the momentum of the cannon?

A motorboat starts from rest and moves with uniform acceleration, if it attains the velocity of 15 m/s in 5s, calculate the acceleration and the distance travelled in that time.

An athlete is running on a circular track. He runs a distance of 400 m in 25 s before returning to his original position. What is his average speed and velocity?

Explain recoil and recoil velocity. Derive its expression.

The launching of a rocket is based on Newton’s third law of motion.

Newton’s first law of motion is called as law of inertia.

Motion is relative.

constant velocity. If that velocity is zero, then the object remains at rest. If an external force is applied, the velocity will change because of the force. The second law explains how the velocity of an object changes when it is subjected to an external force. The law defines a force to be equal to changes in momentum (mass times velocity) per change in time. Newton also developed the calculus of mathematics, and the “changes” “expressed in j the second law are most accurately defined in differential forms. (Calculus can also be used to determine the velocity and location variations experienced by an object subjected to an external force.) For an object with a constant mass the second law states that the force F is the product of an objects mass and its acceleration a:
F = m * a
For an external applied force the change in velocity depends on the mass of the object.

A force will cause in velocity; and likewise, a change in velocity will generate a force. The equation works both ways.
The third law states that for every action (force) in nature there is an equal and opposite reaction. In other words, if object A exerts a force on object B, then object B also exerts an equal force on object: A. Notice that the forces are exerted on different objects. The third law can be used to explain the generation of lift by a wing and the production of thrust by a jet engine

(i) A chalk kept on the table remains in the position of rest until moved by the teacher. Which law of motion is followed in this situation?
(ii) What will happen to momentum if the mass and acceleration both are doubled?
(iii) What will happen to momentum if the mass and acceleration both are halved?
(iv) A moving stone filled truck collides with a moving car coming from opposite direction. Why is it observed that only the car is pushed backward?
(v) What will happen to the force if the jet engines do not produce enough thrust to push the aeroplane in mid-air?

(a) When a bat strikes a ball, the ball exerts an equal and opposite force on the bat. The force : acting on the ball projects it with high velocity, Due to the large mass of bat compared to ball, reaction force on the bat slows down the bat’s motion.
(b) When a bullet is fired from a gun, the gun exerts a force on the bullet in the forward direction. This is the action force. The bullet also exerts an equal force on the gun in the backward direction. This is the reaction force. Due to the large mass of the gun, it j moves only a little distance backward. This backward movement of the gun is called the recoil of the gun.
(c) In a rocket, burning fuel creates a push on the front of the rocket pushing it forward. This creates an equal and opposite push on the exhaust gas backwards.

(i) Which of Newton’s law examples are given here?
(ii) When a rifle is fired it is pushed back this movement is called what?
(iii) What does the ball acquire after it gets velocity?
(iv) State newton’s 1st law of motion.
(v) Which force is required to produce motion in an object?

Explain : State the law of conservation of momentum and derive the formula.

Explain : Explain Newton’s second law of motion and derive the formula.

Explain : Newton’s third law of motion.

balls have masses of 50 gm and 100 gm and they are moving along the same line in the same direction with velocities of 3 m/s and 1.5 m/s respectively. They collide with each other and after the collision, the first ball moves with a velocity of 2.5 m/s. Calculate the velocity of the other ball after collision.

A person travels a distance of 72 km in 4 hours. Calculate average speed in m/s.