Part X Flashcards
AP1.1.A What are scalars?
Quantities that are described by a magnitude alone.
Examples include: speed, mass and distance
AP1.1.A What are vectors?
Quantities that are described by a magnitude and direction.
Examples include: velocity, momentum, force, weight, acceleration and displacement
AP1.1B Know and be able to interpret vector notation
AP1.2.AB How do you resolve a vector into two components at right angles to each other or find the resultant of two vectors at any angles to each other?
By drawing or by using trigonometry.
By drawing or by using trigonometry to split the components into perpendicular forces and Pythagoras’s theorem.
AP1.3.A What is a moment defined as?
Force × perpendicular distance from the point to the line of action of the force.
AP1.3.B Be able to calculate the moment of a force about a point
AP1.3.C What is the principle of moments?
When a body is in equilibrium, the total clockwise moment about a point equals the total anticlockwise moment about the same point.
AP1.4 What are the contact forces?
The normal force which is perpendicular to the surface.
The friction force which opposes the direction of motion.
AP1.5 What conditions are needed for a particle to be in equilibrium?
When the resultant of all forces acting on the particle is zero.
AP1.6 What does smooth and rough mean?
Smooth: friction does not need to be taken into account.
Rough: friction does need to be taken into account.
AP1.7.AB What is the centre of gravity?
The point at which the weight of a body acts through.
This is along the line of symmetry on symmetrical bodies.
AP1.8.A Solve problems involving equilibrium of rigid bodies under coplanar forces (zero resultant force and zero resultant moment):
a. These problems could involve an object on an inclined plane, with or without friction.
AP1.8.B Understand and apply the representation of forces using a triangle of forces.
AP2.1 Understand graphical methods involving distance, displacement, speed, velocity, acceleration and time.
AP2.2 Use graphical representation of 1-dimensional motion to make various deductions (for example, find the displacement from a velocity–time graph).
AP2.3 What are the suvat equations?
v=u+at
s = ut + 1/2at^2
s=((u+v)t)/2
v^2 =u^2 +2as
AP2.4 What is the equation linking velocity, power and force?
power = force × velocity
AP3.1 What are Newton’s laws?
1: A body will remain at rest or at a constant velocity unless acted on by a resultant force.
2: F=ma.
3: Every action has an equal and opposite reaction.
AP3.1 How is terminal velocity reached?
Initially, the only force acting on the object is it’s weight so it’s velocity increases. As it accelerates, they impact with the particles in the air. Due to Newton’s third law this means the particles will have an increasing upwards force on the object. This is air resistance. As velocity and air resistance increase, due to Newton’s second law, the resultant force and rate of acceleration decreases. When weight is equal to drag, the resultant force is zero so the object has reached a maximum and constant velocity.
AP3.2 Model a body moving vertically, or on an inclined plane, with constant acceleration.
AP3.3.A What forces are acting in projectile motion?
No forces in the horizontal direction.
Weight in the vertical direction.
AP3.3.B What are the effects on air resistance on projectile motion?
The air resistance lowers the speed of an object in trajectory. Due to this, the time an object takes to reach the ground is increased. It is also responsible for changing the trajectory path of the object.
AP3.4 Solve simple problems involving two bodies connected by a light inextensible string or rod.
a. For example, two bodies connected by a string over a light smooth pulley or a car towing a caravan.
AP3.4.B Interpret and use free body diagrams.
AP4.1 What is the definition of linear momentum?
Linear momentum is a vector quantity defined as the product of the mass of an object and its velocity.
AP4.2 What are elastic collisions and inelastic collisions?
Elastic collisions: where there is no loss of kinetic energy.
Inelastic collisions: where there is a loss of kinetic energy.
Momentum is conserved in all collisions.
AP4.3 How can the conservation of momentum be related to Newton’s laws of motion.
Force = rate of change of momentum (change of momentum / change in time)
AP4.4 What is the impulse of a force?
The impulse of a force, measured in Ns, is equal to the change in momentum of a body which a force causes. This is also equal to the magnitude of the force multiplied by the length of time the force is applied.
impulse = F∆t = change of momentum
AP5.1.A What are the equations for gravitational potential energy, kinetic energy and work done?
Gravitational potential energy = mg∆h
Kinetic energy = 1/2 mv^2
Work done = Fd
AP5.1.B What is the principle of conservation of energy?
Energy cannot be created or destroyed only transferred from one store to another.
AP5.2 How can power be expressed?
Power = rate of doing work = rate of energy transfer, P = ∆W / ∆t = Fv
AP5.3 What is the equation for efficiency?
Efficiency = useful energy transfer / total energy input × 100%
AP6.1 What is the equation for density?
Density = mass / volume
AP6.2 What is the equation for pressure?
Pressure = normal force / area
AP6.3 What is stress and consequently the types of deformation which could occur?
Stress is an internal force per unit area, and the deformation the object undergoes due to the stress is the strain. Tensile means there is an increase in length of the object, and compressive is a decrease in length.
AP6.5 How could one find the spring constant k?
k = force per unit extension (F/e)
k is therefore also the gradient of a force-extension graph.
AP6.6 What is stress, strain and ultimate tensile strength?
Stress = force / area
Strain = ΔL / L
Ultimate tensile strength shows the maximum amount of stress a material can handle.
UTS = maximum load / original area
AP6.7 What is the equation for Young’s modulus?
Young modulus (Pa) = stress (Pa) / strain
AP6.8 How can strain energy be found?
Strain energy is the energy stored in an elastic body under loading.
It is the area under the force extension graph.
strain energy = 1/2 Fx = 1/2 1/2 kx^2
AP7.2 What is path difference and phase difference?
Path difference is the difference in the path traversed by the two waves.
Phase difference is the difference in the phase angle of the two waves.
AP7.4 What is the equation linking frequency and wavelength?
speed = frequency x wavelength
AP7.6 What is the principle of superposition?
When two or more waves cross at a point, the displacement at that point is equal to the sum of the displacements of the individual waves
AP7.7 How are stationary waves formed?
Standing waves are formed by the superposition of two coherent waves of the same frequency (with the same polarisation and the same amplitude) travelling in opposite directions.
AP7.8 What are nodes and antinodes?
Nodes are the points of no displacement on a standing wave. Antinodes are the points of maximum displacement on a standing wave.
The distance between any two adjacent nodes or antinodes is half a wavelength.
AP7.10 What is the equation for the refractive index?
n = v1 / v2 = sin(x1) / sin(x2)
AP7.11 What is the equation for the critical angle?
n = 1 / sin(C)
AP8.1 What is the equation for charge?
Charge = current x time
AP8.2 What is the equation for potential difference?
pd = work done / charge
AP8.34 What is Ohm’s Law?
voltage = current x resistance
AP8.5 What are the equations for power?
P = VI
P = I^2 R
P = V^2 / R
AP8.6 What are the V-I characteristics of semi-conductor diodes?
In the positive direction, after a small threshold voltage, there’s an exponential increase. In the negative direction no current is let through until a voltage breakdown.
AP8.8 What is the equation for resistivity?
resistivity = rersistance x area / length
AP8.11 What is emf?
emf is the work done in driving unit charge around a complete circuit. (emf = work done / charge)
AP8.11A What is the difference between emf and pd?
The electromotive force is the amount of energy given to each coulomb of charge. The potential difference is the amount of energy utilised by one coulomb of charge. The electromotive force is independent of the circuit’s internal resistance. The potential difference is proportional to the circuit’s resistance.
AP8.11B What is the terminal potential difference?
The terminal potential difference is the potential difference across the terminals of a cell. If there was no internal resistance, the terminal pd would be equal to the emf If a cell has internal resistance, the terminal pd is always lower than the emf.
