This is all the content required for physics paper 2. Each topic/lesson subheading has a link to either a cognito or Free Science lessons video. This doc states if the topic is triple content. Also includes required practicals.
Physics paper 2 video notes
FORCES
Scalar and vector quantities:
- Scalar quantities: mass, temperature, speed, energy, distance, time.
- Scalar quantities have magnitude (size) only.
- Vector quantities: displacement, weight, force, velocity, acceleration, momentum.
- Vector quantities have magnitude and direction.
Contact and non-contact forces:
- All forces take place when two objects interact.
- Contact force is when two objects are physically touching. Tension is an example of
a contact force. Examples of contact forces include friction, air resistance, tension
and normal contact force.
- Air resistance is a contact force because of the collisions between an object and air
particles.
- Non-contact forces – the objects are physically separated. Examples of non-contact
forces are gravitational force, electrostatic force and magnetic force.
- Displacement is the difference between her starting point and end point.
Gravity and weight:
- Weight is the force acting on an object due to gravity. The force of gravity close to the
Earth is due to the gravitational field around the Earth.
- The weight of an object depends on the gravitational field strength at the point where
the object is.
- The weight of an object and the mass of an object are directly proportional. Weight is
measured using a calibrated spring-balance (a newton meter).
Resultant forces:
- The resultant force is the overall force acting on an object, taking into account all the
different forces acting on it. To work out the resultant force, we subtract the smaller
force from the larger force. It will also act in the direction of the greater force.
- Two properties that might be affected by the resultant force is speed and direction.
- If all the forces acting on an object balance out, then we say that the object is in
equilibrium.
Vector diagrams:
- Free body diagrams use arrows to show all the forces acting on an object. The length
of each arrow indicates the magnitude of that force. The direction of each arrow
indicates the direction of the force.
Resolving forces:
Work done and energy transfer:
Forces and Elasticity:
- When we apply a force at either end of an elastic material, these stretching forces
are equal in magnitude but opposite in direction. These forces are balanced. These
forces cause the object to stretch and when the forces are released the elastic object
returns back to its original length. Elastic materials will always return to their original
length or shape if we take away the forces acting on them.
- When we are applying squeezing forces (into the object), the material compresses.
When the forces are released the elastic object returns back to its original length.
, - If an object returns to its original shape after the forces have been removed, it is
known as elastic deformation.
- If an object does not return to its original shape after the forces have been removed,
it is known as inelastic deformation.
- Two forces are required to stretch, compress or bend an object.
- An object’s spring constant is a measure of how many newtons of force it would
require to stretch (or compress) the object by 1 metre. It has the units N/m. It is a
measure of how stiff the object is. Objects with a higher spring constant are more stiff
so they require more force to stretch.
- Hooke’s Law states that the extension of an object is directly proportional to the force
applied. F = ke. F is force, k is spring constant, e is the extension.
- If you stretch an object too much it can pass its 'limit of proportionality. At this point it
will start deforming inelastically.
- When a spring is stretched, energy is transferred to its elastic potential energy store.
Then when the spring is released, most of that energy is transferred to kinetic
energy.
Moments (triple):
- The turning effect of a force is called the moment of the force.
- The unit of moment is Nm.
- The turning effect of the force is centred around the pivot which is the centre of the
nut.
- The distance must be perpendicular from the pivot to the line of action of the force.
Balanced moments (triple):
- For the object to be balanced, the clockwise moment must equal the anticlockwise
moment.
Levers and gears (triple):
- Levers are transmitting the turning effect of the force from one side of the pivot to the
other. Levers are force multipliers.
- Gears can also transit the turning effect of a force. The gear system will transmit the
turning force from the engine to the wheels. The turning effect depends on the
distance between the edge of the gear and the centre.
- When two gears are connected, the gears turn in opposite directions.
- The ratio of the turning effect of the two gears is proportional to the ratio of the radius
of the two gears. For example if the radius of gear B is twice the radius of gear A,
then the turning effect of gear B is also twice the size of the turning effect of gear A.
Pressure in fluids (triple):
- In a gas, the particles are colliding with each other and with the walls of the
container. When the particles collide with the walls, they exert a force. That force is
acting at right angles to the wall.
- Particles in a liquid exert a force at right angles to the walls of the container.
Scientists call gases and liquids fluids.
- The atmosphere is most dense at the surface of the Earth. At the earth’s surface
there are the greatest number of air molecules in a given volume. The atmosphere
gets less dense as we increase in altitude (move away from the surface of the Earth).
The pressure of the atmosphere is caused by air molecules colliding with a surface.
As a surface increases height above ground level, the number of air molecules above
the surface decreases which means that atmospheric pressure decreases with an
increase in height. This explains why mountain climbers often take a supply of
, oxygen with them because the air pressure on a mountain may be too low to supply
all the oxygen they need.
Floating or sinking (triple):
- If we had holes in a container filled with water, water squirts out but the bottom hole
squirts out much further than the water from the top hole. That is because the water
at the bottom of the container is at a higher pressure than the water at the top.
- Factors which determine the pressure exerted by liquid are the depth, density and
gravitational field strength.
- Imagine an object immersed in water. The pressure of a liquid depends on the depth.
The bottom of the object is at a greater depth than the top of the object. The bottom
of the object experiences a larger pressure than the top. Because of this, there is a
larger force acting on the bottom of the object than at the top of the object. There is a
resultant force acting upwards. This resultant force is called upthrust. For an object to
float the upthrust must equal the object’s weight. If the upthrust is less then the object
sinks.
- Upthrust is caused by the pressure on the bottom of the object being greater than the
pressure on the top of the object.
- When we lowered the object, the level of the water rose because the object displaced
the water. The size of the upthrust acting on the object is the same as the weight of
water displaced by the object. If an object can displace its own weight of water then
the upthrust will equal the object’s weight and the object will float.
- An object that is less dense than water will only have to displace a small volume of
water before the weight of water displaced equals the weight of the object. Now the
upthrust equals the weight of the object and the object floats. In this case, the object
floats high in the water.
- An object that has the same density as water, the object has to displace its own
volume of water in order for the weight of water displaced to equal the weight of the
object. Once again the upthrust equals the weight of the object and the object floats.
In this case, the surface of the object is at the surface of the water.
- An object that is more dense than water cannot displace a volume of water equal to
its own weight. Therefore the weight of the object is greater than upthrust so the
object sinks.
Speed:
- Normal walking speed = 1.5 m/s
Running speed = 3 m/s
Cycling speed = 6 m/s
- A younger, fitter person will generally be able to achieve a faster speed than an older
or unfit person. The speed also depends on the terrain, e.g. people move more
rapidly on flat ground than moving uphill. People who are running a long distance
tend to run faster at the start, when they are less tired.
- Cars = 13 m/s
Train = 50 m/s
Aeroplane = 250 m/s
Sound in air = 330 m/s
- Sound travels faster on warmer days than cooler ones.
Velocity:
- Velocity = distance / time
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