Remediation Blog 1

Hello Learners,

Welcome to the class. Today, we will discuss Motion and Force and laws of Motion.
Enjoy your class.

                                             MOTION

Speed is the distance travelled by an object in unit time is referred to as speed. It is represented as                                                                  

• 

Acceleration:

2. Second Equation of Motion:

(Position-Time Relation)

3.  Third Equation of Motion:

Speed of an Object Moving on a Circular Path:

WORKSHEET TO PRACTICE:

1. A train is travelling at a speed of 60 km/ h. Brakes are applied so as to produce a uniform acceleration of −0.5 m /s2. Find how far the train will go before it is brought to rest.

2. A particle was at rest from 1 a.m. It moved at a uniform speed 50km/hr from 1.30 a.m. to 2:00 a.m. Find the average speed between
(a) 1.00 a.m. and 2.00 a.m.
(b) 1.15 a.m. and 2.00 a.m.
(c) 1.30 a.m. and 2.00 a.m.

3. An object moves along a circular path of diameter 14cm with constant speed. If it takes 2 min. to move from a point on the path to the diametrically opposite point. Find
(a) The distance covered by the object
(b) The speed
(c) The displacement
(d) average velocity.

4. A particle with a velocity of 2m/s a t=0 moves along a straight line with a constant acceleration of 0.2m/s2. Find the displacement of the particle in 10s?

5. A particle is pushed along a horizontal surface in such a way that it starts with a velocity of 12m/s. Its velocity decreases at a uniform rate of 0.5m/s2.
(a) Find the time it will take to come to rest.
(b) Find the distance covered by it before coming to rest?

                                FORCE AND LAWS OF MOTION

A push or pull on a body is called force. The direction in which a body is pushed or pulled is called the direction of force.

Force are used in our everyday actions like pushing, pulling, lifting, stretching, twisting and pressing.

Effects of Force

A force cannot be seen. A force can be judged only by the effects which it can produce in variation bodies or objects around us. A force can produce the following effects:

(i)                 A force can move a stationary body.

(ii)               A force can stop a moving body.

(iii)             A force can change the speed of a moving body.

A force can change the direction of a moving body.

NEWTON’S LAWS OF MOTION

Newton has given three laws to describe the motion of bodies. These laws are known as Newton’s Laws of motion.

Newton’s First Law of Motion: According to Newton’s first of motion, A body at rest will remain at rest, and a body in motion will continue in motion in a straight line with a uniform speed, unless it is compelled by an external force to change its state of rest or of uniform motion.

Inertia: Inertia is that property of a body due to which it resists a change in its state of rest or of uniform motion.

MOMENTUM

The momentum of a body is defined as the product of its mass and velocity.

Momentum = mass X velocity

p = m X v; the SI unit of momentum is kilogram metres per second.

Newton’s Second Law of Motion:  The rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction in which the force acts.

                         Force= Change in Momentum

                                                  Time taken

Newton’s Third Law of Motion

 Newton’s third law of motion describes the relationship between the forces that come into play when the two bodies interact with one another. According to Newton’s third law of motion: Whenever one body exerts a force on another body, the second body exerts an equal and opposite force on the first body.

CONSERVATION OF MOMENTUM

According to the law of conservation of momentum: when two bodies act upon one another, their total momentum remains constant provided no external forces are acting.

Worksheet for Practice

   1. What is the change in momentum of a car weighing 1500 kg when its speed increases from 36 km/hr to 72km/h uniformly?

       2.    A truck starts from rest and rolls down a hill with constant acceleration. It travels a distance of 400m in 20s. Find its acceleration. Find the force acting on it if its mass is 7 metric tones.

       3.  A bullet of mass 10g is fired from a gun of mass 6kg with a velocity of 300m/s. Calculate the recoil velocity of the gun.

4.       The car A of mass 1500kg, travelling at 25m/s collides with another car B of mass 1000kg travelling 15m/s in the same direction. After collision the velocity of car A becomes 20m/s. Calculate the velocity of car B after the collision.

5.       A bullet of mass 10g moving with a velocity of 400m/s gets embedded in a freely suspended wooden block of mass 900g. What is the velocity acquired by the block?