# Physics P2

### Description

Flashcards on Physics P2, created by Sophie Weldon on 05/14/2016.
Flashcards by Sophie Weldon, updated more than 1 year ago
 Created by Sophie Weldon over 8 years ago
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## Resource summary

 Question Answer What can forces do? Can cause changes to the shape or motion of an object Resultant force A number of forces acting at a point may be replaced by a single force that has the same effect on the motion as the original forces all acting together. Called the resultant force. If resultant force on stationary object is Zero? Greater than zero? Is zero- object will remain stationary Greater than zero- object will move If resultant force on moving object is Zero? Greater than zero? Zero- continue to move is same direction and speed Greater than zero- move faster in the same direction Acceleration The rate at which a body increases in speed. It is the change in velocity Acceleration of an object is determined by? The resultant force acting on the object and the mass of the object The acceleration of an object is given by the equation: Final velocity - initial velocity / time taken Stopping distance Distance traveled by vehicle during the driver’s reaction time + distance traveled under the braking force thinking distance + braking distance. Stopping distance depends on: The distance the vehicle travels during the drivers reaction time The distance the vehicle travels under the braking force. Things which affect thinking distance: Tiredness Drugs (e.g. alcohol, cannabis, medication which is not ‘non-drowsy’. Distractions (e.g. car too full of passengers, loud music, eating, drinking, smoking) Things which affect braking distance: Road conditions (surface type, gradient, up-keep, leaves) Weather conditions (ice, water) Vehicle condition (regular maintenance, brake condition, tyre condition) Terminal velocity When the forces from a free falling object balance and there is no resultant force. The object falls at a constant speed. Kinetic energy The energy possessed by an object due to movement. Momentum A measure of the state of motion of an object (mass x velocity) Potential energy Energy that is stored. Velocity The speed an object moves in a particular direction. Velocity-time graph Gradient represents acceleration. Distance-time graph Gradient represents speed. Why do we get static electricity? It’s all due to charge. An atom is made from a nucleus which contains protons and neutrons and electrons which spin around the nucleus in orbit. How is static electricity caused? The movement of electrons. Electrons can be rubbed from a surface (making it more positive) or added to a surface (making it more negative). Why can the electrons move in the metal? The electrons in the metal are called ‘free’ or ‘delocalised’ electrons. They do not have to stick with one particular metal atom – they can move freely. The flow of the electrons in the wire around a circuit is called the CURRENT. What is electric current? Current is the flow of electrons around a circuit. An ammeter measures the flow of current around the circuit. Its measured in amps (A). The symbol for current is the letter I. Current = charge / time. Series circuit The current is the same anywhere in the circuit. Parallel circuit The current can change after ‘junctions’. Why do the electrons flow around the current? The current only flows when it is connected to a power source. The power source (e.g. a battery) provides the electrons with a push to get them moving around the circuit. Potential difference Potential difference is measured in volts. Voltmeters measure the P.D between two points in a circuit. Potential difference = (work done) energy transferred/Charge Direct current (d.c.). Cells and batteries supply current that always passes in the same direction. Alternating current (a.c.) Is a current that is constantly changing direction. What mains electricity supply in the UK? It has a frequency of 50 cycles per second (50 hertz) and is 230 V. Live wire The live wire which carries the electricity to the appliance. Is brown Neutral wire The neutral wire which carries the electricity away from the appliance. The wire is blue. Earth wire Is connected to the ground under a house so electricity can be discharged safely. It has yellow and green strips Fuse It is connected to the live wire. Each fuse is rated for a certain current. A fuse with a rating of 13A would met if 13A tried to flow through it. The smaller the rating the thinner the wire in the fuse. If you needed a current of 10A flowing through an appliance you would use a 13A fuse. When the fuse melts, the circuit is broken and electricity cannot flow through the appliance. This can protect the appliances from electrical surges (e.g. in a thunder storm). Residual current circuit breaker (RCCB) A RCCB is connected to the live wire. It does not heat up, instead it detects changes in the current. The RCCBs detect a difference in the current between the live and neutral wire. If the values are not the same there must be a problem and the current is switched off. They work more quickly than fuses. They can also be reset and used again. Gamma ray Is a high energy electromagnetic wave emitted by a nucleus. It’s relative mass is zero. It’s relative charge is zero. Number of protons and neutrons does not change.

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