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A pull or push which changes or tends to change the state of rest or of uniform motion or direction of motion of any object is called force. Force is the interaction between the object and the source (providing the pull or push). It is a vector quantity.
Effect of resultant force:
1 newton =105
Kilogram force (kgf)
The force with which earth attracts a 1 kg body towards its centre is called kilogram force, thus
Dimensional Formula of force: [MLT-2]
For full information of force we require
Force exerted by one particle on the other because of the electric charge on the particles is called electromagnetic force.
Following are the main characteristics of
It acts between any two masses kept anywhere in the universe. It follows inverse square rule
(F ∝ ) and is attractive in nature.
The force mg, which Earth applies on the bodies, is gravitational force.
It is the strongest force. It keeps nucleons (neutrons and protons) together inside the nucleus inspite of large electric repulsion between protons. Radioactivity, fission, and fusion, etc. result because of unbalancing of nuclear forces. It acts within the nucleus that too up to a very small distance.
1.4 Contact force:
Forces which are transmitted between bodies by short range atomic molecular interactions are called contact forces. When two objects come in contact they exert contact forces on each other.
1.4.1 Normal force (N):
It is the component of contact force perpendicular to the surface. It measures how strongly the surfaces in contact are pressed against each other. It is the electromagnetic force. A table is placed on Earth as shown in figure.
Here table presses the earth so normal force exerted by four legs of table on earth are as shown in figure.
Now a boy pushes a block kept on a frictionless surface.
Here, force exerted by boy on block is electromagnetic interaction which arises due to similar charges appearing on finger and contact surface of block, it is normal force.
A block is kept on inclined surface. Component of its weight presses the surface perpendicularly due to which contact force acts between surface and block.
Normal force exerted by block on the surface of inclined plane is shown in figure.
Force acts perpendicular to the surface
Motion of a car on a level curved road
Forces acting on the car,
Free Body Problems
Friction is the force which develops at the surface of contract of two bodies and opposes (impedes) their relative motion.
Hence, m = tan θ
i.e. the limiting friction is equal to tangent of the angle of friction.
Kinetic Friction / Dynamic Friction
Fk ∝ R.
Or Fk= mkR
Fk = F
Momentum = Mass × Velocity
p=m × v
1 N = 1 kg. m/s
Change in momentum
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