An object will remain at rest or continue to travel with constantvelocity unless acted upon by a resultantforce.
Newton’s third law
When two objects interact, they exertequal and oppositeforces on each other. These forces are always the same type and have the same magnitude but they act on differentobjects and in oppositedirections.
newton’s third law example
The gravitational attraction of the earth to a person standing on it, which is equal and opposite to the gravitational attraction of the person to the earth.
four fundamental forces
gravitational, electromagnetic, strong nuclear and weak nuclear
Newton’s second law
The net force acting on an object is directlyproportional to the rate of change of momentum and is acting in the same direction.
Linear momentum of an object is the product of the object’s mass and its velocity. Its SI unit is kgms^-1
F=ma is a special case of newton’s second law and is true when the mass of the object remains constant during the motion of the object.
Impulse of a force is a measure of change in momentum.
conservation of momentum
For a system of interacting objects, the total momentum in a specified direction remains constant as long as no externalforces act on the system.
perfectlyelasticcollision
total kinetic energy of system remains constnt
inelasticcollision
some kinetic energy lost to other forms, eg heat and sound energy. Total energy and momentum are conserved.