SP8a - What is work done?
The energy transferred by a force as it moves an object in the direction of a force.
SP8a - What is the equation for work done?
E = F x d
(Energy = Force x distance moved)
SP8a - What is the equation for Power?
P = E ÷ t
(Power = Energy ÷ time)
SP8a - What is the unit for power?
W - Watts
(Equivalent to J/s - Joules per second)
SP9a - What do you call forces between objects that are touching?
SP9a - What is the name for the regular upward force form the ground when you're standing?
Normal contact force
SP9a - What are the three non-contact forces?
- Gravitational fields
- Static electricity
SP9a - What do all objects that produce a non-contact forces have?
A force field.
An area around an object in which another object could experience a force.
SP9a - Describe how the gravitational pull between the earth and the moon are action-reaction forces.
- Force is a vector quantity.
- The force of the moon on the earth is the same size as the earth on the moon but they are in opposite directions.
- Neither objects move in the direction of the force.
SP9c - What is the formula for a moment?
Moment (N m)
Force (N) x distance perpendicular to the pivot (m)
SP9c - What could you say when weights around a pivot are balanced?
It is in equilibrium
SP9c - What is the principle of moments?
The some of clockwise moments = the sum of anti-clockwise moments
[When a system is in equilibrium]
SP9b - How do you work out the direction and size of the resultant force using the component forces?
The Parallelogram method:
- (If the start of a diagram hasn't already been provided, draw to the two forces using a scale)
- Draw another pair of dashed-lines parallel to the forces
- This should form a parallelogram
- Draw a line from the object to the vertically opposite corner
- Measure this line and use the scale to work out the size
- If required, measure the angle to show the direction
SP9b - How do you resolve the component forces using the resultant force?
The Rectangle method:
- Draw faint horizontal and vertical lines fom the object
- Measure the angle from the horizontal/vertical that the object is at
- Using a scale, draw a line the represent this force
- Draw lines down and across from where this line ends to the horizontal and vertical respectively
- Measure out the length from the object to each of these poitns
- Use the scale to work out the size
SP9c - Explain why using two different sized gears in a car may be beneficial.
- The first smaller gear can be connected to the motor where it recieves the moment
- This passes on an equal force to the second larger gear
- Since the second gear is larger, it will have a larger radius.
- This means that its the distance from the pivot will be greate
- Therefore it will have a larger moment (turnign force) as M = F x d
SP9c - Why is a longer lever more effective?
- The formula for a moment (the turning force) is M = F x d
- Thus, by increasing the distance form the pivot, you will either:
- Increase the turning force
- Decrease the force required to produce the same turning force
SP10a - Describe the structure of an atom including features of the sub-atomic particles.
- Proton and neutron in the nucelus, each with a relative mass of 1.
- Protons have a charge of +1.
- Electrons orbit in energy levels each with a charge of -1 and a relative mass of 1/1835 (negligible)
SP10a - Descirbe what a potential difference is.
The force that pushes the electrons to flow around the circuit.
SP10a - What is conventional current?
What we refer to as the direciton of current from positive to negative. Opposite to the flow of electrons.
SP10a - What are the two types of circuits?
- Series: everything connected in one route
- Parallel: many options for different routes.
SP10a - Why may parallel circuits be more beneficial?
- If the circuit becomes incomplete along one path, the rest of the circuit can still continue to function. (e.g - Switches can be connected to different parts meaning lights in parallel to each other can be switched in and off individually)
- If a bulb goes off, the rest of the circuit in parallel to this can still continue to function
SP10b - What is the unit for current and how can it be measured?
Amps (Amperes). Measured using an ammeter which is attached in series to the circuit
SP10b - What is the unit for potential difference and how can it be measured?
Volts. Measured using a voltmeter which is attached in parallel to the component you are measuring the potential difference of.
SP10b - How does total current differ in parallel and series circuits?
- S: The total current is the same at all points throughout the circuit
- P: The total current gets split between the branches of the circuit, inversely proportionate to the resistance of the components in those branches.
SP10b - How does potential difference differ in parallel and series circuits?
- S: The p.d is different across different components, directly proportionate to the resistance of that component
- P: The p.d is tha same at all points across the circuit
SP10c - What is current?
- The flow of electrons
- The rate of flow of charge
SP10c - What is the unit for charge?
C - Coulombs
SP10c - What is the equation linking charge and current?
Q = I x t
(Charge = Current x time)
SP10c - What equation links energy and charge and how can this be changed to link energy to current?
E = Q x V (Energy = Charge x p.d)
since Q = I x t, this means that
E = I x t x V (Energy = Current x time x p.d)
SP10d - What is Ohm's law?
V = I x R
(p.d (V) = Current (A) x Resistance (Ω))