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55 Cards in this Set
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Average Speed: •Equation •Definition |
Average Speed = Distance travelled/time
v=∆x/∆t
The rate of change of distance of an object calculated over a complete journey |
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Average Velocity: •Equation •Definition |
Average velocity = change in displacement/ time taken
v = ∆s/∆t
For a return journey v=0 as s=0
The change in displacement for a journey divided by the time taken |
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Distance-time graph: •Description •Characteristics |
Straight line (Horizontal) - Stationary
Straight line, with gradient - Constant speed, gradient = speed, a=0
Curve - Varying speed |
Straight line? Gradient? Curve? |
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Displacement-time graph: •Description •Characteristics |
Straight line (Horizontal) - Stationary
Straight line, gradient - Constant velocity, gradient = velocity, a = 0
Curve - Varying velocity |
Straight line? Gradient? Curve? |
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Velocity-time graph: •Description •Characteristics |
Straight line (Horizontal) - Constant velocity, a = 0
Straight line, gradient - constant acceleration, gradient = a
Curve - Varying acceleration
Area = displacement |
Straight line? Gradient? Curve? Area? |
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Stopping Distance |
Total distance travelled from when the driver first sees a reason to stop, to when the vehicle stops
Stopping Distance = Thinking Distance + Braking Distance |
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Thinking Distance: •Definition •Equation |
The distance travelled from when the driver first sees a reason to stop, to when they use the brake
Thinking Distance = speed × Reaction Time |
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Braking Distance |
The distance travelled from the to me the brake us applied until the vehicle stops |
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Free Fall |
The motion of an object accelerating under gravity with no other force acting on it |
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Acceleration of free fall |
The rate of change of velocity of an object falling in a gravitational field. Given on earth as, g (9.81 ms^-2) |
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Terminal Velocity |
The constant speed reached by an object when the drag force (and upthrust) is equal and opposite I the weight of the object |
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Three stages of free fall (Describe the motion of a sky diver as the leave an aircraft) |
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Net force/resultant force? Acceleration? |
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Moment: •Equation •Definition |
The product of the force and the perpendicular distance from a pivot or stated point
Moment =Fx Moment = Force × perpendicular distance of the line of action of a force from the axis or point of rotation |
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Principle of Moments |
For a body in rotational equilibrium, the sum of the anticlockwise moments about any point is equal to the sum of the clockwise moments about that same point |
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Couple |
A pair of quality and opposite forces on a body but not acting in the same straight line |
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Torque: •Equation •Definition |
The moment of a couple
Toque = Fd Torque of a couple = one of the forces × perpendicular separation between the forces |
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Density |
Density = mass/volume
ρ = m/V Mass per unit volume kgm^-3
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Pressure |
Pressure = Force/Area P = F/A Force exerted per unit cross sectional area kgm^-1s^-2 = Nm^-2 = Pa |
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Pressure in Fluids: •Equation •Proof |
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Archimedes' Principle |
The upthrust exerted on a body in a fluid, whether partially or fully submerged, is equal to the weight of the fluid displaced and acts in the opposite direction |
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Work done: •Definition of work •Equation •Realtion to energy |
The product of the force and the distance moved in the direction of the force Work done = force × distance moved in direction of force W = Fx Work done = Energy Transferred |
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Energy |
The capacity for doing work (J) |
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Kinetic Energy |
Energy due to motion of an object with mass
KE = (mv^2)/2
KE = 1/2 × mass × velocity^2 |
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Gravitational Potential Energy |
Energy of a an object with mass due to its position in a gravitational field
GPE = mgh
GPE = mass × acceleration of free fall × height
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Chemical Energy |
Energy contained within the helical binds between atoms - can be released when atoms are rearranged |
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Elastic Potential Energy |
Energy stored in an object as a result of a reversible change in its shape EPE = Fx/2 EPE = 1/2 × average force × final extension Or: as F=kx EPE = (kx^2)/2 |
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Nuclear Energy |
Energy stored within the nuclei of atoms |
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Radiant Energy (EM Energy) |
Energy associated with all the electromagnetic waves, stored within oscillating electric and magnetic fields |
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Sound Energy |
Energy of mechanical waves due to the movement of atoms |
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Internal Energy (Heat or Thermal) |
The sum of the random potential and kinetic energies of atoms in a system |
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Power |
The rate at which work is done (W)
Power = work done/time
P=W/t
W = Js^-1 = kgm^2s^-3 |
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Equation for energy efficiency |
Efficiency (%) = (useful energy output/total energy input) × 100 |
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Hooke's Law |
The extension of a spring is directly proportional to the force applied until the elastic limit of the spring is exceeded
F=kx Force = force constant × extension |
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Force-extension Graph for Metal Wire |
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Force-extension Graph for Rubber |
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Force-extension Graph for Polythene |
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The area under a force extension graph is equal to |
Work done
∆W = F×∆x |
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Equivalent spring constant for springs in parallel |
k(eqv) = k(1) + k(2) |
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Equivalent spring constant for springs in series |
1/k(eqv) = 1/k(1) + 1/k(2) |
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Tensile Stress |
Force per cross sectional area on a material (Pa)
Stress = Force/cross sectional area
σ=F/A |
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Tensile strain |
The extension per unit length of a material, a dimensionless quantity
Stain = extension/original length
Ɛ = x/L |
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Stress-Strain graph for a ductile material |
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What are points: P,E, Y1, Y2, UTS,B? |
P - limit of proportionality, stress and strain no longer proportional E - Elastic limit, elastic deformation up to this point, plastic for any further Y1 Y2 - Upper and lower yield points, material extends rapidly UTS - ultimate tensile strength, maximum stress a material can withstand while being stretched before it breaks. Necking occurs beyond this point B - Breaking point, stress value is known as breaking stress |
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Necking |
Process by which a material elongates and narrows at its weakest point due to stress above the materials UTS |
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Young Modulus |
The ratio of tensile stress to tensile strain when these quantities are directly proportional (Pa)
Young modulus = tensile stress/tensile strain
E = σ/Ɛ
The gradient of the linear section of a Stress-Strain graph |
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Stress-Strain Graph for Rubber |
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Stress-Strain Graph for Polythene |
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Newton's First Law |
A body will remain at rest it continue to move with constant velocity unless acted upon by an external force |
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Newton's Second Law |
The net resultant force ring in an object us directly proportional to the rate of change of its momentum, and is in the same direction F = ∆p/∆t For an object of constant mass: F= (mv-mu)/t = m(v-u)/t F=ma |
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Newton's Third Law |
When two objects interact, they exert equal and opposite forces on each other |
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Momentum |
Momentum = mass × velocity p=mv |
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Conservation of Momentum |
For a system of interacting objects, the total momentum in a specific direction remains constant as long as there are no external forces acting on the system |
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Perfectly Elastic Collisions: What is conserved? •Momentum •Total Energy •Total KE |
Momentum - Conserved Total Energy - Conserved Total KE - Conserved |
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Inelastic Collisions: What is conserved? •Momentum •Total Energy •Total KE |
Momentum - Conserved Total Energy - Conserved Total KE - Not Conserved |
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Impulse |
The product if force and the time over which the force acts (Ns) Impulse = F × ∆t F = ∆p/∆t Therefore, Impulse = change in momentum |
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