BTEC Applied Science Unit 5 physics

What are the standard units of mass, length and time?

Kilograms, metres and seconds

What are the SI prefixes for 10^3, 10^6 and 10^9?

kilo, mega, giga

What are the SI prefixes for 10^-3, 10^-6 and 10^-9?

milli, micro, nano

What is work done?

The energy transferred in moving something

What is power?

the rate at which work is done

What happens to a gas when it is compressed?

Particles get closer together
Gas pressure increases
More collisions between particles and container
Temperature of gas rises

How do you calculate work done from a P-V graph?

The area under the graph

What is efficiency?

the percentage of the work input that becomes useful work output

What is thermal equilibrium?

when two objects have the same temperatures and net heat transfer is zero

What is the first law of thermodynamics?

The change in a system's internal energy is equal to the difference between heat added to the system from its surroundings and work done by the system on its surroundings

What are ideal gases?

All collisions are elastic
All motion is random
There are no forces between particles

What is absolute zero?

0 K
Particles have 0 kinetic energy

What is the second law of thermodynamics?

Heat will not flow from a colder body to a hotter one without an input of work. A natural process cannot fully be reversed.

What is an isothermal process?

a process that occurs at constant temperature

What is an adiabatic process?

no thermal energy is transferred between the system and its surroundings.

What is the Carnot cycle?

an idealised engine cycle

What is a heat pump?

Gas goes into the compressor. The compressor squashes the gas to make it hot. The condenser converts the gas into a liquid. The potential energy lost by the particles is released as heat.
The expansion valve slows down and spreads out the liquid, like an aerosol, which cools it down
The evaporator takes in energy from the surroundings to evaporate the liquid back to a gas.

Define specific latent heat.

the energy required to change the state of unit mass of the substance without change of temperature.

Define specific heat capacity

energy (in kJ) required to heat one kg of substance by one kelvin

How do you find the density of an irregular solid?

Measure mass using balance. Measure volume by looking at amount of water displaced. Mass / volume.

Define Hooke's Law

The extension of a spring is directly proportional to the force applied

What is the elastic limit?

The maximum amount a material can be stretched by a force without permanently deforming

Give examples of malleable and brittle materials

Malleable - layers of atoms able to slide eg copper
Brittle - fracture under stress due to layers of atoms eg glass.

Define stress

the force per unit area applied to a material

Define strain

the ratio of the extension of a material compared to the original length

Explain how rubber behaves when it is stressed.

Initially hard to stretch, then strain increases, then before it breaks becomes more difficult to stretch again because the bonds are all stretched out

What is elastic hysteresis?

A property where strain lags behind stress when the material is loaded and then unloaded.

What is streamlined flow?

all the lines of flow are parallel. The speed of flow is fastest in the centre and slowest near the sides.

What is turbulent flow?

Turbulent flow happens because of drag. Drag or any objects in the fluid interrupt the smooth flow, rotate parts of the liquid and absorb kinetic energy.

What is an aerofoil?

The air going above must take the same time to travel to the other side of the aerofoil as the air going below it, but it has further to travel. This means it travels faster. Because it travels faster, it exerts less pressure. This means there is a lift force upwards.