• A force is either a push or pull that one body exerts on another body.
• The forces can be classified into two natures:
• Contact forces, which exist between objects that are in contact.
• Non-contact, which does not require objects to be in contact.
Contact forces:
Normal reaction
Friction
Tension.
Non-contact forces:
Gravitational force
Electric force
Magnetic force
A force is a vector and has both magnitude and direction. Newton (N) is the S.I unit of force.
• When two parallel forces are added, a resultant force is formed, which produces the same effect as two combined.
• The Addition of non-parallel vectors is done by the parallelogram method or tip-to-tail method.
• Force can cause the body to speed up, slow down, change state, and change direction.
• Newton's first law states that every object will continue its state of rest or uniform motion in a straight line unless a resultant force acts on it.
• Newton's second law states that when a resultant force acts on an object of a constant mass, the object will accelerate in the direction of the resultant force.
• The product of mass and acceleration gives Force.
F=ma
The S.I unit of force is the newton.
• Newton's third law states that if body A exerts a force on Body B. then Body B will exert an equal and opposite force on body A
• To every action there is an equal and opposite reaction
• Friction is a contact force that opposes or tends to oppose the motion between surfaces in contact.
Advantages of friction:
• help in walking smoothly
• Moving vehicles can slow down
Disadvantages of friction:
• make cars less efficient by 20%
• energy losses
• Wheels, Ball bearings, lubricants, and polished surface and air cushion to reduce Negative effects
• Treads, Parachutes, and chalk to enhance positive effects.
• Air resistance is a type of friction in the air. To speed up, the skydiver reduces air resistance by adopting the head-first position. To reduce speed he increases air resistance by adopting a spread eagle position. To land safely he made use of a large surface area of a parachute.
• Drawing a free-body diagram helps us to visualize the forces acting on a body.
• Braking distance increased on wet roads because of less friction, less deceleration, and less opposing force.
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