BTEC applied science Unit 5 Physics

What is Hooke's Law?

When a spring stretches, the extension of the spring is proportional to the force stretching it, provided the elastic limit of the spring is not exceeded.

Equation for Hooke's law

F=K x e

What do the letters stand for in the hookes law equation

F= Force in newtons (N)
K=Spring constant in newtons per meter (N/m)
e= Extension in meters (m)

When deforming materials, what is the point called where it will no longer return to its original shape

Elastic limit

A spring with 10,000 n/m extends 10cm, how much force was applied?

F=Ke
F=10,000 x 0.1
F=1,000N

Steps for working out a maths question in Physics.

1 Write out the equation
2. Substitute
3.Calculate
4.Units

What is the difference between heat anf temperature

Temperature - Kinetic energy of particles (Vibrating)
Heat- is energy (J)

What is specific heat capacity

Specific heat capacity is the amount of energy needed to change the temperature of 1kg of a substance by 1 degree celcius without changing state.

Units do q=mC∆T

Q= Energy in JM= mass in kilograms C=Specific heat capacity∆T= Change in temperature ( degrees C)

How do you work out gradient

change in y/change in x

What is Power?

the rate at which work is done

Power( W)=

Energy transfer (J)/Time (S)

Efficiency

The efficiency of an energy transfer is the proportion of the input energy that becomes useful output energy.

Efficiency=

Useful energy output / total energy input

terminal velocity

When a object falls it must move the fluid around it. This causes an upwards drag force which acts against the movement of the object.

What is Bernoulli's principle?

As the flow rate of a fluid increases the pressure at right angle to thee flow decreases.

Types of energy

mechanical energy, electrical energy,chemical energy,nuclear energy,thermal energy

Types of energy pathways

EM-radiation Electric current Mechanical waves

How do you transfer kelvin in to Celsius

-273

How do you transfer celsius to kelvin ?

+273

Springs in series

Springs arranged one after an other
Double the extension
each string will extend the same amount as they are both under the same amount of weight.

Springs in parallel

the weight is distributed evenly between parallel springs

tensile strength

A measure of how much stress from pulling, or tension, a material can withstand before breaking.

Equation for tensile stress

Stress= Force (N) / Area (M2)

Example question- A 10g log pen dangles from a human hair of diameter 10 micrometers. What is the stress?

Force+ 0.01 x 10= 0.1 N
Area = Pi x R2
Pi x (5X10 -6)= 7.85 x 10 -13M
Stress =Force/ Area
0.1/7.85 x 10 -3
=1.27 x 10 power of 11 Pa

Stain =

Change in length/ original length

Young's Modulus

stress ( Pa)/strain (Unitless)

Work done =

force x distance

What does the area between the lines on a load and extension graph of rubber show ?

Area between curves shows energy loss to thermal - count the squares.

Fatigue

By repeatedly loading and unloading a material we can microscopic defets. Continuing to load and unload the material makes these defects larger. This makes the material brittle and it will fracture .

Creep

All materials have particles moving with a distribution (Temperature ) . of energies.

What affects how fast a fluid flows down an incline?

Friction,
Temperature,
Material of the surface ,
gradient,
Viscosity of the fluid,
Depth of fluid

The Lower the viscosity the ....

Less friction there is between each layer

The deeper the fluid the greater the....

Number of joints between layer to slide past each other

What is vaminar flow

Vaminar flow is when the fluid stays in neat layers and moves along

What happens if there is an object in the way of the laminar flow ?

Turbulence occurs

What happens if fluid tries to flow too quickly

The frictional force between the laminar can cause the fluid at that point to move up or down .

Terminal velocity

When an object falls it must move the fluid around it . This causes an upwards drag force which acts against the movement of the object.

Bernoulli's Principle

as the velocity of a fluid increases, the pressure exerted by the fluid decreases

Efficiency

The efficiency of an energy transfer is the proportion of the input energy that becomes useful out put energy

Efficiency=

Useful output / total input

What is the difference between heat and temperature?

Temperature- Kinetic energy of particles ( Vibrating )
Heat- Is energy

What is specific heat capacity?

The amount of energy required to increase the temperature of 1kg of a substance by 1oC

cooling curve graph