physics topic test

S.I. units

S.I. units

length: metres (m)
mass: kilograms (kg)
time: seconds (s)

distance:

how far you have travelled

displacement:

a straight line distance between the finishing and starting point (displacement specifies distance and direction)

Scalar quantity:

has a size (magnitude) but not direction
e.g., distance, mass, time.

Vector quantity:

has a size (magnitude) and direction
e.g., displacement, force, velocity.

vector drawings:

• use arrows to represent vectors

• several of these vectors are drawn together; vector diagram.

• the vector is drawn point in the direction of the vector with a north point/compass.

• vector (arrows) must touch.

• provide a size (magnitude) and direction for your resultant vector.

  • 1st direction, angle, 2nd direction.

• draw the diagram (always a right triangle).

Speed:

a measure of how quickly something moves.
→ speed = distance/time
→ S.I. units is m/s

Velocity:

how displacement changes with time and must have direction.
→ velocity: displacement/time

motion:

change in position measured by distance and time.

Acceleration:

measure of the rate at which velocity changes
→ measured in m/s-2

Force:

a push, pull or a twist that can change an objects motion.
→ change in speed, direction and shape.
→ measured in Newtons (N)

Resultant force:

combination of all forces that are acting on an object
→ if forces act together, add them
→ if forces are opposing, subtract them

Inertia:

a force is needed to get something moving
force required to change the speed or direction of something that is already moving
tendency to resist any object in motion is called an object’s inertia.
that larger the mass of an object, the greater its inertia; the harder it is to change its motion.

Newton’s first law

→ an object at rest will remain at rest unless it is acted upon by a force.
→ an object that is moving will continue to move at the same speed and in the same direction unless an unbalanced force acts upon it.

Newton’s second law

→ the force acting on an object is equal to the mass of the object multiplied by its acceleration.

F = m * a

weight:
mass:

the gravitational force acting on an object
the overall matter in an object that doesn’t change.

Newton’s third law

for every action force, there is an equal and opposite reaction force.

Work:

when a force is applied to an object and makes it move some distance, considered done if energy is transferred or transformed.
S.I. unit: Joules (J)

energy:

the ability to do work and the transfer of energy to cause a change.
S.I. unit: Joules (J)

Kinetic energy:

energy of movement

types of kinetic energy:

• heat: movement of atoms

• sound: vibrations of atoms

• light: moving waves of energy

• electrical: moving electrons

potential energy:

energy which is stored and has potential to cause movement.

types of potential energy:

• chemical: energy stored in chemicals

• gravitational: energy stored due to height

• elastic: energy stored due to objects being stretched/squashed.

• nuclear: energy stored in nuclei of atoms

Law of conservation of energy

Energy cannot be created or destroyed; it can only be transferred or transformed.

energy transfer:

energy transferred from one object to another.

energy transformation:

1 type of energy is transformed into another type of energy.

Power:

rate that work is done, or how fast energy is used
→ measured in watts (W)

efficiency losses:

most energy transformations result usually as an undesirable efficiency loss as thermal energy.