Topic 1 - physics Flashcards
Scalar
A physical quantity that has magnitude but no direction. Example: speed, volume and mass.
Vector
A physical quantity that has both magnitude and direction. Example: displacement, velocity and acceleration.
Resolving vectors
When 2 or more vectors are causing an effect, they can be resolved into a resultant vector. The resultant vectors magnitude and direction shows the overall effect caused by all the components.
Density
Density is a measure of an objects mass per volume.
Finding volume
Volume can be found using a ruler and geometry
example: volume of a cuboid is AxBxC
Finding volume through an irregular object can be done by measuring the amount of water it displaces.
Newtons Laws
1st law: An object in motion will stay in motion and an object in rest will stay in rest unless acted on by an outside force.
2nd law: F=ma (explained more in topic 1 formula’s)
3rd law: Every action has an equal and opposite reaction.
Mass
Refers to the amount of matter that makes up an object. (kg)
Weight
The force on an object due to gravitational field. (N)
Hooke’s law
Hooke’s law states that the amount of force applied to an elastic object is proportional to how far it stretches. However, if the object is overstretched it will not spring back. Hooke’s Law only applies if an elastic object is not overstretched.
(not my definition)
Circular motion
When an object moves in a circle it’s constantly changing direction, as velocity is a vector, a change in direction means a change in velocity. Due to the acceleration formula, this change in velocity means the object is accelerating and therefore must be experiencing a force.
Moments
Moments refers to a turning effect on an object about a pivot point.
A spanner can be used to maximise the turning effect needed to loosen a bolt.
Centre of mass/gravity
Point where gravity or weight appears to act through.
For regular shapes the centre of mass is the geometric centre of the object.
For irregular shapes, the object mass must be hung of different points and a vertical line drawn directly down.
Momentum
Momentum is always conserved.
In order to change momentum a force must be involved.
Collisions
Elastic collisions: kinetic energy and therefore momentum is fully conserved.
Inelastic collisions: kinetic energy and therefore momentum is not conserved due to energy losses in other forms. For example heat and sound.
If momentum is conserved, it means the total momentum before the collision is equal to the total momentum after the collision.
Impulse
Impulse describes a change in the momentum of an object. It also describes the forces involved during the change in momentum.
Energy
Energy is the ability to do work.
Energy stores:
Kinetic
Gravitational potential
Elastic potential (strain)
Nuclear
Electrostatic
Thermal (internal kinetic)
Energy transfers:
Mechanical (forces)
Electrical
Heating
Electromagnetic, sound or other waves
eg) GpE —> kE + thermal
Thermal produced sound waves.
Kinetic energy
The energy of moving objects
Conservation of energy
Energy cannot be created or destroyed. It can only be transformed from one store to another.
Gravitational potential
Energy stored when an object is raised to a height within a gravitational field.
Work
The term ‘work’ is used to describe a transfer of energy.
If an objects energy changes we say “work has been done:”
Power
Defined as the rate at which work is done, or the rate of energy transfer.
Power is measured in watts (w). This is equivalent to Joules per second (J/s)
Boiler
Uses heat from the burning of fuels to boil water into steam.
Turbine
Transforms thermal energy from a fluid (liquid or gas) into rotational kinetic energy.
Generator
Consists of coil (or coils) of wire that rotate in a magnetic field to produce an electrical current.
Sources of electricity production
Hydroelectric
wind
tidal/waves
solar
fossil fuels
nuclear
geothermal
bio fuels
Energy efficiency
No energy transfer is 100% efficient. There is always some energy lost.
Pressure
Pressure is a measure of force per area.
The SI unit for pressure is the pascal (Pa) which is essential N/m².
SI - system international.
Pressure in liquids
Liquid pressure is the increase in pressure at increasing depths in a liquid.
