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Force
Force, Newton's third Law and acceleration
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Force is a convenient abstraction to represent mentally the pushing and pulling interaction between objects.
The unit of force is the Newton (N) - where one newton is one kilogram metre per second squared. Th enewton is defined as the force which, when applied to a mass of one kilogram, gives an acceleration of one metre per second squared.
F = m a (1)
where
F = force (N)
m = mass (kg)
a acceleration (m/s2)
It is common to express forces as vectors with magnitude, direction and point of application. The net effect of two or more forces acting on the same point is the vector sum of the forces.
Newton's Third Law
Newton's third law describes the forces acting on objects interacting with each other. Newton's third law can be expressed as
- "If one object exerts a force F on an other object, then the second object exerts an equal but opposite force F on the first object"
Acceleration
If there is a net unbalance between forces acting on a body the body accelerates. If the forces are balanced the body will not accelerate.
Example - Force needed for Acceleration
A mass of 50 kg is accelerated at 2 m/s2. The force required can be calculated as
F = (50 kg) (2 m/s2)
= 100 N
Example - Force due to Gravity
The force on a mass of 50 kg due to gravity 9.81 m/s2 can be calculated as
F = (50 kg) (9.81 m/s2)
= 490.5 N
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