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Unit 1 Physics as
| Question | Answer |
|---|---|
| scalar | A physical quantity with magnitude ( size) but not direction e.g. speed, distance, pressure, potential difference, density, energy |
| vector | A physical quantity with magnitude ( size) and direction e.g. velocity, acceleration, force. |
| Displacement | Distance travelled in a particular direction. Therefore a vector. |
| Instantaneous speed | The speed of an object at a given moment in time. |
| Average speed | A measure of the total distance travelled in a unit of time Average speed =Distance/time |
| Velocity (v) | Displacement per unit time Average velocity = displacement/ time= s/t |
| Acceleration (a) | The rate of change of velocity. Acceleration= change in velocity/ time a= ∆v/∆t a= ((v-u))/t |
| Newtons second law | Net force = mass x acceleration F=ma |
| The newton | Unit of force. 1N is the force that gives a mass of 1kg an acceleration of 1ms-2 |
| Drag | The resistive force that acts on a body when it moves through a fluid |
| Weight (W) | The gravitational force acting on an object measured in newtons Weight = mass x acceleration due to free fall W=mg |
| Terminal velocity | The velocity at which an object’s drag equals its accelerating force. Therefore there is no resultant force and zero acceleration |
| Equilibrium | When the net force and net moment on an extended object is zero |
| Centre of gravity | This is the point where the entire weight of an object appears to act |
| Triangle of forces | If three forces acting at a point can be represented by the sides of a triangle, the forces are in equilibrium |
| Couple | This is a pair of forces that tends to produce rotation only. They are two forces that are equal in size but act in opposite directions but not in the same straight line. |
| Torque of a couple | The turning effect due to a couple Torque = one of forces x perpendicular distance between the forces. Torque = Fd |
| Moment of a force | The turning effect due to a single force. Calculated from the force multiplied by the perpendicular distance from a given point Moment = force x perpendicular distance from a given point (pivot/fulcrum). Moment = Fx |
| Principle of moments | For a body in rotational equilibrium the sum of the clockwise moments equals the sum of the anticlockwise |
| Density | The mass per unit volume Density=m/V |
| Pressure(p) | Force per unit area Note 1Pa=1Nm-2 P=F/A |
| Thinking distance | The distance travelled from seeing the need to stop to applying the brakes. |
| Braking distance | The distance travelled by a vehicle whilst decelerating to a stop. |
| Stopping distance | The distance a vehicle travels while decelerating to stop.The sum of the thinking distance and braking distance. |
| Crumple zone | An area of a vehicle designed to increase the distance over which the vehicle decelerates and so reduce the average force acting. |
| Work done by a force(W) | The product of the force and the distance moved in the direction of the force Note. Work is done when energy is transfer of energy . W= Fx or W = Fx Cosθ |
| The joule | This is a unit of energy. 1 J is the work done when a force of 1N moves its point of application 1m in the direction of the force. |
| Conservation of energy | States that energy cannot be created or destroyed , just converted from one form to another or transferred from one place to another. |
| power | Rate of work done Power = workdone/time Power=(energy transfer)/time |
| The watt | A unit of power. 1 watt is 1J of energy transferred per second |
| efficiency | The ratio of useful output energy to total input energy State that the efficiency of a device is always less than Efficiency= (useful output energy)/(total input energy) x |
| Tensile force | Usually two equal and opposite force acting on a wire in order to stretch it. When both forces have to value T , the tensile force is T not 2T |
| Compressive force | Two or more forces that have the effect on reducing the volume of the object on which they are acting or reducing the length. |
| Extension(x) | The change in length of an object when subjected to a tension. |
| Elastic limit | The point at which elastic deformation becomes plastic deformation. |
| Limit of proportionality | The point at which an object no longer obeys Hooke’s Law |
| Hooke’s law | The extension of an elastic body is proportional to the force that causes it. F=kx |
| Force constant(k) | Force per unit extension or compression. |
| Elastic potential energy | The energy stored in a stretched or compressed object (e.g. a spring) E = ½ Fx E= ½ kx^2 |
| stress | The force per cross-sectional area. Stress=force/(cross sectional area) Stress = F/A |
| strain | The extension per unit length Strain = extension/length Strain =x/l |
| Young’s modulus (Y) | The ratio between stress and strain. Y =stress/strain |
| Ultimate tensile strength | The maximum tensile force that can be applied to an object before it breaks. |
| Breaking stress | The maximum stress that can be applied to an object before it breaks. |
| Elastic deformation | The object will return to its original shape when the deforming force is removed |
| Plastic deformation | The object will not return to its original shape when the deforming force is removed, it becomes permanently deformed. |
| Ductile material | Materials that have a large plastic region and can therefore can be drawn into a wire e.g. copper |
| Brittle material | A material that distorts very little even when subject to a large stress and does not exhibit any plastic deformation e.g. concrete. |
| Polymeric material | A material made of many smaller molecules bonded together, often making a tangle knot of chains e.g. rubber. These materials often exhibit very large strains e.g. 300% |
Created by:
stumpy7780
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