single force that has the same - Freesciencelessonsfreesciencelessons.co.uk/wp-content/uploads/2016/04/Unit-2-Physics... · forces all acting together? If the resultant force acting

Page 1 Remember that you are given equations in the exam (but not the units)

When two objects interact, the forces they exert on each other are …………… and

…………………..

When several forces act on an object, what do scientists call the single force that has the same

effect on the motion as the original forces all acting together?

If the resultant force acting on a stationary object is zero,

what will happen to the motion of the object?

If the resultant force acting on a stationary object is not

zero, what will happen to the motion of the object?

If the resultant force acting on a moving object is zero, what

will happen to the motion of the object?

If the resultant force acting on a moving object is not zero,

what will happen to the motion of the object?

What is the equation linking the acceleration of an object to its mass and the resultant

force acting on it?

What is shown by the gradient of a distance-time graph?

What is meant by the velocity of an object?

What is the equation for the acceleration of an object?

What is shown by the gradient of a velocity-time graph?

When a car is moving, what is the main force opposing the

motion of the car?


When several forces act on an object, the single force that has the same effect on the motion as

the original forces all acting together is called the resultant

force.

When two objects interact, the forces they exert on each

other are equal and opposite.

If the resultant force acting on a stationary object is not

zero, the object will accelerate in the direction of

the resultant force.

If the resultant force acting on a stationary object is zero,

the object will remain stationary.

If the resultant force acting on a moving object is not zero, the object will accelerate in the direction of the resultant

force.

If the resultant force acting on a moving object is zero, the object will continue to move a the same speed and in the

same direction.

The gradient of a distance-time graph shows the speed

of the object.

a = F / m

where a = acceleration (m/s2), F = force (N), m = mass (kg)

acceleration (m/s2) = final velocity (m/s) - initial velocity (m/s)

time taken (s)The velocity of an object is its speed in a given direction.

When a car is moving, the main force opposing the motion of the car is air-

resistance.

The gradient of a velocity-time graph shows the

acceleration of the object.


When a car is moving at a constant speed, what can we say about the air-resistance

compared to the driving force?

What happens to the braking force needed to stop a vehicle

if the vehicle is moving at a greater speed?

What do we call the distance that a vehicle travels while the driver reacts before braking?

What do we call the distance that a vehicle travels while the

driver is braking?

State three factors that can affect a driver’s reaction time.

State three factors that can affect a vehicle’s braking

distance.

What happens to the temperature of a vehicle’s

brakes when the brakes are applied?

When an object moving through air or a liquid

increases its speed, what happens to the friction force

acting on the object.

Describe what happens to the motion of a parachutist from

leaving the airplane to landing.

What is the equation used to calculate the weight of an

object?

What do we call the type of energy stored in a stretched

spring?

What is the link between the force applied to a spring and the extension of the spring?


If a vehicle is moving at a greater speed, the braking

force needed to stop the vehicle increases.

When a car is moving at a constant speed, the air-resistance balances the

driving force?

The distance that a vehicle travels while the driver is

braking is called the braking distance.

The distance that a vehicle travels while the driver reacts

before braking is called the thinking distance.

Three factors that can affect a vehicle’s braking distance are:

• poor road conditions• poor weather• brakes not maintained properly

Three factors that can affect a driver’s reaction time are:

• tiredness• drugs• alcohol

When an object moving through air or a liquid

increases its speed, the friction force acting on the

object increases.

When the brakes are applied, friction between the brakes and the wheel reduces the kinetic

energy of the vehicle. The temperature of the brakes

increases.

weight (N) = mass (kg) x gravitational field strength (N/kg)

• The force of gravity causes the parachutist to accelerate at the start.

• As the speed increases, the air-resistance increases.• When air-resistance balances the force of gravity, the

parachutist reaches terminal velocity (steady speed).• When the parachute is opened, air resistance increases and

the parachutist decelerates, slowing down.• As the parachutist slows, air resistance decreases until it

balances gravity. The parachutists now has a (slower) terminal velocity until they land.

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

the limit of proportionality is not exceeded).

The type of energy stored in a stretched spring is called elastic potential energy.


What is the equation for work done?

What is the equation for power?

What is the equation for gravitational potential

energy?

What is the equation for the kinetic energy of an object?

What is the equation for the momentum of an object?

What is meant by the conservation of momentum?

Why do insulating materials become electrically charged

when they are rubbed together?

If a material loses electrons, what happens to the charge on

the material?

If a material gains electrons, what happens to the charge on

the material?

What happens when two objects with the same type of

charge are brought close together?

What happens when two objects with different types of

charge are brought close together?

What is meant by an electrical conductor e.g. metals.?


Power (W) = Energy (J) time (s)

work done (J) = force (N) x distance (m)

Ek = 0.5 x m x v2

Ek = kinetic energy (J)m = mass (kg)v = speed (m/s)

Ep = m x g x h

Ep = change in gravitational potential energy (J)

m = mass (kg)g = gravitational field strength (N/kg)

h = change in height (m)

The conservation of momentum tells us that the total momentum before an event is equal to the total

momentum after an event.

p = m x v

p = momentum (kg m/s)m = mass (kg)

v = velocity (m/s)

If a material loses electrons, the material becomes positively charged.

When insulating materials are rubbed together, electrons (which are negative) are

rubbed off one material and onto the other.

When two objects with the same type of charge are

brought together, there is a force of repulsion between

the objects.

If a material gains electrons, the material becomes negatively charged.

An electrical conductor (eg metals) allows electrical charge to move easily

through it.

When two objects with different types of charge are

brought close together, there is a force of attraction between

the objects.


What equation links the electrical current with the flow

of charge?

What is the equation linking potential difference (voltage)

and work done per coulomb of charge?

What is the momentum of an object that is not moving?

What is shown by this symbol?

What is shown by this symbol? What is shown by this symbol?





V = W Q

V = potential difference (V)W = work done (J)

Q = charge (C)

I = Q t

I = current (amperes A)Q = charge (coulombs C)

t = time (seconds s)

This symbol shows an open switch

An object that is not moving has zero momentum.

This symbol shows a lamp (bulb)

This symbol shows an closed switch

This symbol shows a cell

This symbol shows a fuse

This symbol shows an ammeter

This symbol shows a diode

This symbol shows a voltmeter

This symbol shows a battery




What is shown by this symbol? This shows the current-potential difference graph for which component?

State the unit for resistance. The current through a resistor at a constant temperature is ……………. ………………. to the potential difference.

What equation links potential difference, current and

resistance?

For a given potential difference, what happens to

the current if we increase the resistance?

What can we say about the potential difference of cells

connected in series.

State three facts about components connected in

series.


This symbol shows a variable resistor

This symbol shows a resistor

This symbol shows a light-dependent resistor (LDR)

This symbol shows a thermistor

This shows the current-potential difference graph for a resistor at a constant temperature.

This symbol shows a light-emitting diode (LED)

The current through a resistor at a constant temperature is

directly proportional to the potential difference.

The unit for resistance is the Ohm (Ω).

For a given potential difference, if we increase the

resistance, the current decreases.

V = I x R

V = potential difference (volts)I = current (amperes)

R = resistance (Ω)

For components connected in series:• The total resistance is the sum of the

resistance of each component.• Each component has the same current

going through it.• The total potential difference of the supply is

shared between the components.

As long as all the cells point in the same direction, the total

potential difference is the sum of the potential differences of

each cell in series.


State two facts about components connected in

parallel.

This shows the current-potential difference graph for which component?

What happens to the resistance of a filament bulb

as the temperature of the filament increases?

This shows the current-potential difference graph for which component?

What are the key features of a diode?

What are the key features of a light-emitting diode (LED)?

Why are LEDs increasingly being used for lighting?

What happens to the resistance of a light-

dependent resistor (LDR) as the light intensity increases?

What happens to the resistance of a thermistor as the temperature increases?

Cells and batteries supply direct current (DC). What is meant by direct current?

Mains electricity is alternating current (AC). What is meant by

alternating current?

What is the frequency of the mains AC current in the UK?


This shows the current-potential difference graph for a filament bulb.

For components connected in parallel:• The potential difference across each

component is the same• The total current through the whole circuit is

the sum of the currents through each component.

This shows the current-potential difference graph for a diode.

As the temperature of the filament increases, the

resistance of a filament bulb increases.

An LED emits light when the current flows through it in the

forward direction.

The current through a diode can only flow in one direction.

The diode has a very high resistance in the reverse

direction.

As the light intensity increases, the resistance of a light-

dependent resistor decreases.

LEDs are increasingly being used for lighting as they use a much smaller current than

other forms of lighting.

In direct current, the current always passes in the same

direction.

As the temperature increases, the resistance of a

thermistor decreases.

In the UK, the frequency of the mains AC current is 50

hertz.

In alternating current, the current is constantly changing

direction.


In the UK, what is the potential difference (voltage) of the mains electricity supply.

What are the names of the three wires found in three-

core electrical cable?

The pins of a three-pin plug are made of brass. Explain

why.

The casing of an electrical plug is made of plastic.

Explain why.

State the colours of the following wires in the UK:

• Live• Neutral• Earth

State the wiring pattern in a three-pin plug in the UK.

What is the purpose of the fuse in a plug?

How does an RCCB work and what is their benefit?

What is the link between the thickness of the cable for an appliance and the value of the

fuse needed to protect it?

Some appliances have double insulation. What does this

mean?

What happens to the temperature of a resistor when an electrical charge (current) flows through it?

What is meant by the power of an appliance?


The three wires found in three-core electrical cable are live,

neutral and earth.

In the UK, the potential difference (voltage) of the mains electricity supply is

around 230V.

The casing of an electrical plug is made of plastic

because plastic is a good insulator, preventing electrical

shock.

The pins of a three-pin plug are made of brass because

brass contains copper which is a good conductor of

electricity.

The wiring pattern for a three-pin plug is:

• Live (brown) to the right connected to the fuse

• Neutral (blue) to the left• Earth (green/yellow) to the centre

Live = BrownNeutral = Blue

Earth = Green / Yellow stripes

An RCCB cuts the current if it detects a difference in the current between the live and neutral wires (eg if the wire is damaged by a lawnmower).

The benefit is that this is much faster than a fuse, reducing the risk of injury.

If an electrical fault causes too great a current, the wire in

the fuse melts and breaks the current, reducing the risk of

injury/death.

An appliance with double insulation does not need an earth connection. The symbol

for double insulation is

The thicker the cable running to an appliance, the greater the fuse value the appliance

will need.

The power of an appliance tells us the rate at which

energy is transferred.

When an electrical charge (current) flows through a

resistor, the resistor gets hot. This heat can be wasted e.g.

in a filament bulb.


State the equation used to calculate the power of an appliance from the energy

transfer.

State the equation used to calculate the current through an appliance from the power

and voltage.

How should we choose the correct fuse for an appliance?

Why can we not use a 3A fuse for an appliance that requires

4A of current?

State the equation used to calculate the energy used by an

appliance (HIGHER TIER).

Describe the earlier “plum-pudding” model of atomic

structure.

Describe how the Rutherford and Marsden alpha-scattering

experiment led to the “plum pudding” model of atoms being

replaced by the “nuclear model”

State the relative mass and charge of protons, neutrons

and electrons.

Why do atoms have no overall charge?

When do we call atoms that have gained or lost

electrons?

What do we call atoms of an electron with a different number of neutrons.

What is meant by background radiation?


P = I x V

P = power in watts (W)I = current in amperes (A)

V = potential difference in volts (V)

P = E t

P = power in watts (W)E = energy in joules (J)t = time in seconds (s)

If we use a 3A fuse for an appliance that requires 4A, then the fuse will instantly

blow, cutting the current. We should use a 5A fuse.

Always use a fuse which has a slightly higher current rating than the current needed by the appliance e.g. if the appliance needs 3A, use a fuse rated 5A.

In the earlier “plum pudding” model, atoms have negative

charges embedded in a cloud of positive charge.

E = V x Q

E = energy in joules (J)V = potential difference in volts (V)

Q = charge in coulombs (C)

Protons have a relative mass of 1 and a charge of +1.

Neutrons have a relative mass of 1 and a charge of 0.

Electrons have a relative mass of 1/2000 and a charge of -1.

• Alpha particles were fired at a thin sheet of gold atoms.• Most alpha particles went straight through, showing that

atoms are mainly empty space.• Some alpha particles bounced straight back, showing

that most of the mass of the atom is in a dense, central nucleus.

• Some alpha particles changed direction as they pass through, showing that the nucleus is positively charged.

Atoms that have gained or lost electrons become ions (atoms

with an overall charge).

Atoms have no overall charge because protons are positive and electrons are negative. The total

number of protons equals the total number of electrons so the charges

cancel.

Background radiation is radiation that is present all

the time due to natural or man-made causes.

Atoms of an element with a different number of neutrons

are called isotopes.


State two natural and two man-made causes of

background radiation.

What is an alpha particle, a beta particle and gamma

radiation?

What happens to the atomic and mass number of an atom

that has undergone alpha decay? (HIGHER TIER).

What happens to the atomic and mass number of an atom

that has undergone beta decay? (HIGHER TIER).

How ionising are alpha, beta and gamma radiation?

Describe the penetrating power of alpha, beta and

gamma radiation.

Describe the deflection of alpha, beta and gamma

radiation in a magnetic or electric field.

Describe the dangers of alpha radiation.

Describe the dangers of beta radiation.

Describe the dangers of gamma radiation.

State a use of alpha radiation. Why is it suited for this?

State a use of beta radiation. Why is it suited for this?


An alpha particle is two protons and two neutrons (the same as a helium

nucleus). A beta particle is an electron from the nucleus. Gamma

radiation is electromagnetic radiation.

Natural causes = rocks and cosmic rays from space.

Man-made causes = nuclear accidents and fallout from

nuclear weapons tests.

When an atom undergoes beta decay, the atomic number

increases by one. The mass number does not change.

When an atom undergoes alpha decay, the atomic

number drops by two and the mass number drops by

four.

• Alpha radiation is stopped by several cm of air or a piece of paper.

• Beta radiation is stopped by a sheet of aluminium 1-2 mm thick.

• Gamma radiation is stopped by several cm of lead or a metre of concrete.

Alpha radiation is the most ionising, beta radiation is

strongly ionising and gamma radiation is the least ionising.

Alpha radiation is too large to penetrate the skin so it is not very dangerous when outside the body.

However, if a source of alpha radiation is inhaled, it can damage the DNA of

cells in the lung, leading to cancer.

• Gamma radiation is not deflected at all as it has no charge.

• Alpha particles are deflected as they have a charge but not very strongly as they have a

large mass.• Beta particles are deflected in the opposite

direction to alpha (as they have the opposite charge). They are strongly deflected as they

have a small mass.

Gamma rays can easily penetrate into the body where they can damage the DNA of

cells and lead to cancer.

Beta particles are small and can penetrate into the body where they are stopped (for example by bone). They can damage the DNA of cells,

leading to cancer.

Beta radiation is used in thickness detectors e.g. in cardboard manufacture. This is because beta particles will be able to penetrate thin cardboard but some may be stopped by thicker cardboard. All alpha

particles would be stopped and no gamma rays would be stopped.

Alpha radiation is used in smoke detectors. This is because the alpha

radiation will not be dangerous to humans as it will not penetrate the plastic case of

the detector. Both beta and gamma radiation would penetrate the case and be

dangerous.


State the uses of gamma radiation.

What is meant by the half-life of a radioactive isotope?

What is meant by nuclear fission.

Which two elements undergo nuclear fission in nuclear

reactors?

What happens during a nuclear fission chain

reaction?

What is meant by nuclear fusion?

What is the name of the process that releases energy

in stars?

What is meant by a protostar?

What happens in a main sequence star?

Describe the life-cycle of stars around the same size as the

Sun.

Describe the life-cycle of stars much larger than the Sun.

What is the heaviest element that can be made by fusion in

stars? How are elements heavier than this made?


The half-life is the time taken for the number of nuclei of that

element to halve, or the time taken for the radioactive count-rate of the

sample to halve.

Gamma radiation is used to treat cancer and to sterilise

equipment (for example syringes used in medicine).

Uranium-235 and Plutonium-239 undergo

fission in nuclear reactors.

Nuclear fission is the splitting of the nucleus of an atom.

In nuclear fusion, two nuclei join together to form a larger

nucleus.

In a nuclear fission chain reaction:• The nucleus of Uranium-235 or

Plutonium-239 absorbs a neutron• The nucleus now splits and releases 2-3

more neutrons and energy• These neutrons can now trigger more

nuclei to undergo fission.

A protostar is a hot, swirling mass of dust and hydrogen gas being

pulled together by gravitational attraction (during this process,

smaller masses may join to form planets).

The process that releases energy in stars is nuclear

fusion.

A main sequence star around the same size as the Sun expands

into a Red Giant. This then shrinks into a White Dwarf and

then into a Black Dwarf.

A main sequence star fuses hydrogen nuclei to make helium,

releasing energy. The expansion forces caused by this are balanced

by the force of gravitational attraction.

The heaviest element that can be made by fusion in stars is iron. Elements heavier than

iron are made in a supernova.

Stars much larger than the Sun explained into a Red Super Giant.

This then explodes into a Supernova. After the Supernova, we have either a

Neutron Star or a Black Hole.

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single force that has the same - Freesciencelessonsfreesciencelessons.co.uk/wp-content/uploads/2016/04/Unit-2-Physics... · forces all acting together? If the resultant force acting