# IB Physics SL - Topic 2: Mechanics

Definition of vector.
They have a magnitude and a direction associated with them
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Definition of scalar.
They have a magnitude but no direction.
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What does the symbol s mean?
Displacement: the distance moved in a particular direction.
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What does the symbol v (sometimes u) mean?
speed: rate of change of distance (speed=distance gone/time taken)
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What does the symbol a mean?
Acceleration: the rate of change of velocity (a=change of velocity/time taken)
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How do you calculate the relative velocity?
Both object travelling on straight line: subtraction or addition.
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Displacement-time graph
Gradient = velocity. Area does not represent anything useful.
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Velocity-time graph
Gradient = acceleration. Area under graph is the displacement.
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Acceleration-time graph
Gradient: rate of change of acceleration, not useful. area under graph: change in velocity.
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How can you practically calculate velocity or acceleration?
*light gates *strobe photography *tick timer
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All forces (9)
*Gravitational force *Electrostatic *Magnetic *normal reaction *friction *tension *compression *upthrust *lift
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Hooke's law
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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## Other cards in this set

### Card 2

#### Front

Definition of scalar.

#### Back

They have a magnitude but no direction.

### Card 3

#### Front

What does the symbol s mean?

#### Back ### Card 4

#### Front

What does the symbol v (sometimes u) mean?

#### Back ### Card 5

#### Front

What does the symbol a mean?

#### Back 