Please enable JavaScript.
Coggle requires JavaScript to display documents.
Physics Paper 2 (Forces (Scalar and Vector quantities:
The direction that…
Physics Paper 2
Forces
Scalar and Vector quantities:
The direction that an object is travelling is important when describing its motion. However, direction is not important for some quantities.
A scalar quantity is a quantity in which direction is not important. All that matters is its magnitude.
A vector quantity is a quantity in which direction is important
Contact and non-contact forces:
Non contact forces are forces that act between two objects that are not physically touching each other. An example of this could be magnets or gravity.
Contact forces are forces that act between two objects that are physically touching each other. An example of this could be a box on a table, or pen on paper.
Gravity:
Gravity is a force that attracts objects towards each other. Any object with mass exerts a force of gravity. The greater the mass, the greater the force. The force of gravity between two objects decreases as the objects move further apart.
- Pulls objects on Earth towards the centre of the planet.
- Holds the Earth's atmosphere in place.
- Holds all the components of the solar system in orbit around the Sun.
- Holds all the components in the galaxy together.
Resultant forces:
- A stationary object remains stationary of the sum of the forces acting upon it is zero.
- A moving object with a zero resultant force keeps moving at the same speed and in the same direction.
- If the resultant force sting on an object is not zero, a stationary object begins to accelerate in the same direction as the force.
- A moving object speeds up, slows down, or changes direction.
Work done & energy transfers:
Work done and energy transferred are measured in joules (J). The work down on an object can be calculated if the force and distance moved are known.
Work done = Force x Distance
Power:
Power is a measure of how quickly work is being down and so how quickly energy is being transferred. Power is measured in watts (W).
Power = Work done / Time
Forces and elasticity:
A force acting on an object may cause the shape of an object to change. Elastic objects can store elastic potential energy if they are stretched. For example, this happens when a catapult is used.
Distance & Displacement:
Displacement is the distance travelled in a straight line. It has both direction and size.
Speed:
The speed of an object tells you how fast or slow it's moving. To work out speed, the following two things must be known:
- The distance travelled.
- The time taken to travel that distance.
Speed = Distance / Time
Velocity:
The velocity of an object is its speed in a particular direction. Acceleration is a change in velocity, this means that an object accelerates if:
- Its speed changes.
- Its direction changes.
- Both its speed and direction change.
Acceleration:
When an object moves in a straight line with a constant acceleration, you can calculate its acceleration if you know how much its velocity changes and how long this takes.a = (v - u) / t
- a is the acceleration of the object in m/s².
- v is the final velocity in m/s.
- u is the initial velocity in m/s.
- t is the time taken in seconds, s.
Newton's three laws:1st Law:
States that objects with balanced forces acting on them will stay at rest or stay in constant motion.2nd Law:
States that when an unbalanced force acts on an object;
- The direction of the objects acceleration is the same as the unbalanced force,
- The magnitude of the objects acceleration varies in direct proportion with the size of the unbalanced force,
- The magnitude of the objets acceleration varies inversely with the mass of the object.
3rd Law:
States that every action has an equal and opposite reaction.
Thinking, braking, and stopping distance:Thinking distance is the distance traveled when the driver realises he needs to brake and actually braking.
Factors that may increase the thinking distance:
- Greater speed.
- Tiredness.
- Alcohol and drugs.
- Distractions.
Braking distance is the distance taken to stop once the brakes are applied.
Braking distance can be increased by:
- Greater speed.
- Poor road conditions.
- Car conditions.
Momentum:
A moving objet has momentum. It is difficult to change the direction of movement of an object with a lot of momentum.p = m v
- p is the momentum in kg m/s.
- m is the mass in kg.
- v is the velocity in m/s.
Conservation of momentum:
As long as no external forces are acting on the objects involved, the total momentum stays the same in explosions and collisions. We say that momentum is conserved
Waves
Transverse & Longitudinal waves:
In transverse waves, the oscillations are at right angles to the direction of travel and energy transfer. Light and other types of electromagnetic radiation are transverse waves. All types of electromagnetic waves travel at the same speed through a vacuum, such as through space.
In longitudinal waves, the oscillations are along the same direction as the direction of travel and energy transfer. Longitudinal waves show area of compression and rarefaction.
Properties of waves:
Amplitude:
As waves travel, they set up patterns of disturbance. The amplitude of a wave is its maximum disturbance from its undisturbed position. (Basically half the whole wave).
Wavelength:
The wavelength of a wave is the distance between a point on one wave and the same point on the next wave. It is easiest to measure from one crest to another.
Frequency:
The frequency of a wave is the number of waves produced by a source each second. It is also the number of waves that pass a certain point each second.
Wave speed:v = f x λ
- V is the wave speed in m/s.
- f is the frequency in Hz.
- λ (lambda) is the wavelength in metres, m.
Electromagnetic waves in order of size (largest to smallest):
- Radiowaves.
- Microwaves.
- Infrared radiation.
- Visible light.
- Ultraviolet.
- X-rays.
- Gamma rays.
Typical Electromagnetic wave uses:
- Radio waves are used for television.
- Microwaves are used for cooking or mobile phones.
- Infrared waves are used for optical fibre communication.
- Visible light is obviously for seeing.
- Ultraviolet is used for detecting forged bank notes.
- X-rays are used for medical images of bones.
- Gamma radiation is used for killing cancer cells.
-
Physics equations
- Weight = mass x gravitational field strength
- Work done = force x distance
- Force applied to a spring = spring constant x Extension
- Distance travelled = speed x time
- Acceleration = change in velocity / time
- Resultant force = mass x acceleration
- Momentum = mass x velocity
- Kinetic energy = 0.5 x mass x (speed)²
- Gravitational potential energy = mass x gravitational field strength x height
- Power = Energy transferred / time
- Efficiency = useful output energy transfer / total input energy transfer
- Efficiency = useful power output / total power input
- Wave speed = frequency x wavelength
- Charge flow = current x time
- Potential difference = current x time
- Power = potential difference x current
- Power = (current)² x resistance
- Energy transferred = power x time
- Energy transferred = charge flow x potential difference
