Up to the elastic limit, the extension, x, of a spring is proportional to the tension force, F. The constant of proportionality is k, the spring constant. Unit: N/m

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Free-body diagram

Only one object is chosen. All forces action on it have to be drawn.

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Newton's first law

An object continues in uniform motion on a straight line or at rest unless a resultant external force acts.

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Define equilibrium.

Resultat force on object equals to zero, it is in translational equilibrium-

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Gravitational force

force between objects as a result of their masses (weight).

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ELECTROSTATIC FORCE

force between object as a result of their electric charges.

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magnetic force

force between magnets or electric currents.

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friction force

the force that opposes the relative motion of two surfaces and acts along the surfaces. air resistance and drag are friction forces.

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tension force

when a string or spring is streched, it has equal and opposite forces on its ends pulling outwards.

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Newton's second law

a resultat force causes an acceleration. (momentum - the resultant force is proportional to the rate of change od momentum)

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Newton's third law

when two bodies a and b interact, the force that a exerts on b is equal and opposite to the force that b exerts on a.

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Momentum

Linear momentum (p) is defined as the product of mass and velocity, p = m * v. unit: m/s

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Impulse

Change of momentum, delta(p) = F delta(t)

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Elastic collision

No mechanical energy lost (only real elastic collision is between molecules). Relative velocity of approach always equals the relative velocity of seperation.

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totally inelastic collision

objects stick together after collision. relative velocity of separation is zero. total momentum is conserved but majority of the mechanical energy is lost.

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inelastic collision

some energy lost, objects don't stick together. momentum is conserved.

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Definition of work

W=Force * distance

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Relationship between work and energy

the amount of energy transferred is equal to the work done. same unit.

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Definition of power

power is the RATE at which energy is transferred. P = W/t (work done/time taken)

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Definition of efficiency

Ratio of useful energy to the total energy transferred.

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Describe uniform circular motion

an object that is going around a circle at constant speed. direction of object is changing all the time = velocity is constantly changing = object is accelerating

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