1. Force2. Newton’s 1st law of Motion3. Inertia4. Types of Inertia5. Momentum6. Newton’s 2nd law of Motion7. Impulse8. Newton’s 3rd law of Motion9. Law of Conservation of Momentum10. Applications of Newton laws of Motion
11. Friction – A necessary evil12. Cause of Friction13. Types of Friction14. Laws of Limiting Friction15. Coefficient of Friction16. Angle of Friction & Angle of Repose17. Advantages & Disadvantages of Friction
Force : It is an external agency which changes or tends to change the state of motion or direction of its motion or the shape of an object is known as force. In layman’s term it is also known as push or pull applied on an object.
*Acc. to newton’s 1st law of motion, an object continues to be in its state of rest or state of motion along a straight line until and unless an external unbalanced force is applied to it.*It is also known as law of inertia.*It also defines force
INERTIAIt is that inherent property of amaterial body by the virtue of which itresists any change in its state of rest orof uniform motion along a straightline.
Types of inerTia1. Inertia Of Rest: An Object Tends To Be In State Of Rest Until & Unless An External & Unbalanced Force Is Acted Upon It.2. Inertia Of Motion: It Is That Inherent Property Of A Material By Virtue Of Which It Resists Any Change In Its State Of Motion.3. Inertia Of Direction: It Is A Inherent Property Of A Material By Virtue Of Which It Resists Any Change In Its Direction Of Motion.
These pumpkins will not move unlessacted on by an unbalanced force.
Once airborne, this ball would not stop unless acted on by an unbalanced force (gravity and air – fluid friction), it would never stop!
Why then, do we observeevery day objects inmotion slowing down andbecoming motionlessseemingly without anoutside force? It’s a force we sometimes cannot see – friction.
NewtoN’s 2Nd Law of MotioN It states that the rate of change of momentum is directly proportional to the force applied and change takes place in the direction of force applied Alternatively, it is also stated as the force is directly proportional to product of mass and acceleration produced by the force.F α m*aF = m*a
2ND LAW When mass is in kilograms and acceleration is in m/s/s, the unit of force is newton (N). One newton is equal to the force required to accelerate one kilogram of mass at one meter/second2
NewtoN’s 3rd Law of MotioN It states that every action has equal and opposite reaction. By newton’s 3rd law of motion Faction=-Freaction
According to Newton,whenever objects Aand B interact witheach other, they exertforces upon eachother. When you sit inyour chair, your bodyexerts a downwardforce on the chair andthe chair exerts anupward force on yourbody.
It states that in an isolated system , the vector sum of the linear momentum of all bodies remains conserved and is not affected by their mutual interaction. i.e. Initial momentum = final momentum m1v1+m2v2=(m1+m2)v3
Newtons 1st Law Because of inertia, objects (including you) resist changes in their motion. When the car going 80 km/hour is stopped by the brick wall, your body keeps moving at 80 m/hour.
Newton’s 2nd Law proves that different massesaccelerate to the earth at the same rate, but withdifferent forces.• We know that objects with different masses accelerate to the ground at the same rate.• However, because of the 2nd Law we know that they don’t hit the ground with the same force. F = ma F = ma 98 N = 10 kg x 9.8 m/s/s 9.8 N = 1 kg x 9.8 m/s/s
Newton’s 3rd Law in Nature Consider the propulsion of a fish through the water. A fish uses its fins to push water backwards. In turn, the water reacts by pushing the fish forwards, propelling the fish through the water. The size of the force on the water equals the size of the force on the fish; the direction of the force on the water (backwards) is opposite the direction of the force on the fish (forwards).
The reaction of a rocket isan application of the thirdlaw of motion. Variousfuels are burned in theengine, producing hotgases.The hot gases push againstthe inside tube of the rocketand escape out the bottomof the tube. As the gasesmove downward, the rocketmoves in the oppositedirection.
When an object moves or tends to move ,that opposing force which comes into playis known as friction.
Causes of friction:
There are three main types of friction: Static friction: the force of friction which comes into play when a body is at rest over the surface of other. Limiting friction: the maximum value of static friction which comes into play when body is at the verge moving. KineticDynamic friction: the force of friction which acts on a actually moving body.
Slide a book across atable and watch itslide to a restposition. The bookcomes to a restbecause of thepresence of a force -that force being theforce of friction -which brings the bookto a rest position.
The force of limiting friction between two bodies in contact is directly proportional to the normal reaction between them i.e. FαR The force of limiting friction is always opposite to the direction in which an object is at the verge of moving. The force of limiting friction is independent of apparent area of contact as far as the normal reaction between them remains the same. The force of limiting friction depends upon nature of surfaces in contact and nature of material of surfaces in contact.
Coefficient of frictionAccording to 1st law of limiting friction:FαRF= μ Rμ=F/RWhere μ is called coefficient of limiting friction and is defined as the ratio of limiting friction to the normal reaction between the two surfaces in contact.
anGle of friction: It is defined as the angle which the resultant of limiting friction and normal reaction makes with the normal reaction
anGle of repose:
ϴ=angle of repose
advantaGes of friction Walking is because of friction No two bodies will stick to each other Vehicle’s braking system works because of friction Nuts and bolts would not be able to hold the machinery together Writing would not be possible Adhesive will loose their purpose
disadvantaGes of friction Friction always opposes motion, therefore extra energy is required to overcome friction Wear and tear of machinery is caused by friction Friction causes production of heat which damages the machinery