Physics

Question 1

Force

Answer 1

Is any interaction that, when unopposed, will change the motion of anobject

Can be an acceleration (push) or deceleration (pull).

Force = mass X acceleration (F=MA kg.m/s-2)
Unit is Newtons (N)

Often the ‘acceleration’ is gravity, which is 9.8m/s-2

Question 2

Pressure

Answer 2

Main application of force to health care

Pressure = force
area
In other words, the force (or weight) pushing or pulling on a particular area.

Note the importance of area in this formula
Large forces over a large area can mean less pressure than a moderate force over a small area

Question 3

Pressure in Solids

Answer 3

Pressure sores (Also called decubitus ulcers)

Weight of a bed-ridden patient is the force they are placing on the bed.
If not moved frequently, only small area of body may actually touch the bed
Eg heels, buttocks
Large force applied to small area → high pressure
Large pressure being applied to one small area may lead to:
Reduction of blood flow to the area
Development of pressure sores
Spreading load over wider area = lower pressure

Question 4

Pressure in liquids

Answer 4

Blood pressure

The beating of the heart creates pressure in blood vessels in order to pump blood throughout the body
Pressure in liquids (& gases) measured by a manometer
Blood pressure measured by a sphygmomanometer (see later in this subject)

Question 5

Pressure in Gases

Answer 5

Breathing

Gases move from an area of higher pressure to an area of lower pressure (wind)
Breathing is about creating areas of higher/lower air pressure in the chest to facilitate air movement into /out of the lungs
This is Boyle’s law:
pressure of a given quantity of gas varies inversely with its volume

Question 6

Heat

Answer 6

The chemical building blocks of our body (atoms & molecules) are not still but are always vibrating.

When heat is applied to molecules and atoms they vibrate more, causing them to expand and also increasing the speed of chemical reactions to occur (sometimes needed for reactions to occur at all) Heating speeds up reactions while cooling slows them down.

The body gets rid of excess heat in part by increasing blood flow to skin. Basis of heat therapy (increased blood flow aids healing)
High heat disrupts the shape of molecules especially proteins, which can kill cells and cause burn injuries including sunburn

This includes killing microorganisms. This is the basis for heat sterilization
Boiling
Hot oven
Autoclave (water under pressure to heat to 122C to kill bacterial endospores)

Question 7

Electricity

Answer 7

Electricity is the flow of charged particles, usually electrons (negative charge) or protons (positive charge) . [see the chemistry topic]. Substances that these particles can flow through are called conductors. Conductors in the body include:
Fluids (containing ions)
Nerve cells
Pacemaker wires etc.
Substances that particles cannot flow through are called insulators. Insulators include
Dry skin offers most resistance (>1million ohm)
Myelin sheath
Plastic covering around machinery & wires

Question 8

Current

Answer 8

is the is the flow of electrical charge in a circuit (measured in Amperes (Amps))

Question 9

Voltage

Answer 9

is the potential difference in charge between two points in an electrical field (volts)
Voltageis the cause andcurrentis its effect.