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77 Cards in this Set
- Front
- Back
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Displacement |
A vector that measures the distance moved by an object relative to a point in space |
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Instantaneous speed |
The speed of an object at a particular instant of time |
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Average speed |
A scalar that measures the distance travelled by an object over a given time |
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Velocity |
A vector that measures the change in displacement of an object over a given time |
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Acceleration |
A vector quantity that measures the rate of change of an object's velocity |
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How to measure instantaneous velocity |
This can be measured by finding the gradient of a line on a displacement-time graph either through a tangent drawn at that point or calculus |
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Gradient of a velocity-time graph |
Acceleration |
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Area under a velocity-time graph |
Displacement |
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Gradient of a displacement-time graph |
Velocity |
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Area under an acceleration time graph |
Velocity |
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Newtons's first law of motion |
A body will remain at rest or continue to move with constant velocity unless acted upon by a resultant force |
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Newtons's second law of motion |
The rate of change of momentum of an object is directly proportional to the resultant force applied to it and takes place in the direction of the force |
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Newtons's third law of motion |
When two objects interact, each exerts an equal but force upon the other during the interaction |
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Momentum euqation |
Momentum = Mass * Velocity (kgms^-1 or Ns) |
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Linear momentum |
The product of the mass and velocity of an object |
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Impulse |
The change in momentum of an object |
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Impulse equation |
Ft = mv - mu (Ns) Where F = net force, t = time, m = mass, v = velocity after collision and u = velocity before collision |
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The area under a force-time graph |
Impulse |
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Conservation of momentum |
The momentum of a closed system will always remain constant |
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Inelastic collision |
A collision where the total kinetic energy of the system changes |
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Elastic collision |
A collision where the total kinetic energy of the system remains constant |
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Measurements taken to calculate g |
Displacement, time, initial velocity |
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Methods to calculate g |
Electromagnet and trapdoor Light gates |
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Thinking distance |
The distance of a driver seeing a reason to stop and applying the brakes |
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Braking distance |
The distance between the driver applying the brakes and the vehicle stopping |
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Stopping distance |
The distance between a driver seeing a reason to stop and the vehicle stopping |
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Thinking distance equation |
Velocity * Reaction time |
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Newton definition |
The amount of force that would give an object of mass 1kg and acceleration of 1ms^-1 |
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Weight equation |
Mass * Gravity |
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Centre of mass |
A point on an object through which any force applied produces a straight line of motion with no rotation |
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Tension |
The pulling force exerted by a string, cable or chain |
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Normal contact force |
The force exerted by a surface on an object, which acts perpendicularly to the surface |
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Upthrust |
The upward buoyant force exerted on a body immersed in fluid
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Friction |
The force of resistance that occurs when one object moves over the surface of that of another |
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Drag |
A frictional force that resists the movement of an object through a fluid |
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The factors that affect drag |
The density of the fluid The texture of the object's surface The speed of the object The cross-sectional area of the object |
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Drag force is directly proportional to |
Speed^2 |
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Terminal velocity |
The point where the drag acting upon an object in free-fall is equal to its weight and therefore it has no acceleration |
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Technique used to measure terminal velocity in a fluid |
By attaching a ball to either end of a pulley system and then placing the heavier one in a fluid, a laser can be used to measure the motion of the other ball |
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Moment |
The product of force and perpendicular distance from a pivot |
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Principle of moments |
For a body in rotational equilibrium, the sum of the anticlockwise moments about a point is the same as the sum of the anticlockwise moments about that point |
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Couple |
A pair of equal and opposite forces acting on a body but not in the same straight line |
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Torque of a couple |
The product of one of the forces of a couple and the perpendicular distance between the two forces |
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Density |
Density = mass / volume The amount of mass in a substance |
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Pressure |
Pressure = Force / Area Pressure is the force applied to an object over an area |
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Archimedes' principle |
The upthrust on an object in a fluid is equal to the weight of the fluid it displaces |
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Pressure exerted by a cylinder of fluid equation |
P = hpg Where h = the height of the liquid column p(ro) = the density of the liquid g = acceleration due to gravity |
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Upthrust equation |
upthrust = Axpg Where A = area of surface of the object x = height of the object p(ro) = density of fluid g = acceleration due to gravity |
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Joule definition |
1 joule is the amount of energy expended to move an object by a force of 1N by 1m. Can also be written as 1Nm. |
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Work done equation |
Work done = Force * Distance moved in direction of force. Units are J or Nm. |
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Forms of energy |
Kinetic Potential |
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Principle of conservation of energy |
The total energy of a closed system remains constant. Energy cannot be created nor can it be destroyed. |
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A falling object's kinetic energy |
In total equal to its original gravitational energy 1/2mv^2 = mgh |
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Kinetic energy equation |
1/2mv^2 |
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Gravitational potential energy equation |
mgh |
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Steps to derive from first principles for kinetic energy on an object starting from rest |
F = ma v^2 = u^2 + 2as thus s = v^2 / 2a Energy transfer is the same as work done thus force * distance KE = v^2/2a * ma KE = 1/2mv^2 |
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Power |
Work done / time The amount of work done over a period of time Since work done is the same as energy transferred it can be described as the rate of energy transfer |
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1 Watt definition |
1W is the same as 1 Joule per second. Also 1Nm per second |
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Power in terms of F and v |
P = Fv Where F is the driving force v is velocity |
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Derive P = Fv |
Work done = Force * Distance P = W / T thus P = Fd / T d / t = velocity P = Fv |
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Efficiency of a mechanical system equation |
(useful energy out / total energy in) * 100 |
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Tensile deformation |
A change in the shape of an object due to tensile forces |
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Tensile force |
Equal and opposite forces acting on an object to stretch it |
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Compressive deformation |
A change in the shape of an object due to compressive forces |
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Compressive force |
Two or more forces acting together that reduce the length or volume of an object |
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Compression |
The decrease in length of an object when a compressive force is exerted on it |
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Springs in series |
Force constant is reduced (halved if two identical springs) Extension is doubled Act as one spring |
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Springs in parallel |
Force is spread between springs thus extension is reduced |
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The condition where Young modulus applies |
Before elastic limit is met |
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Centre of gravity |
The point where weight appears to act in an object |
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Ultimate tensile strength |
The maximum stress that a material can withstand before it breaks |
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Elastic limit |
The value of stress beyond which elastic deformation becomes plastic deformation for a material |
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Elastic deformation |
A reversible change in the shape of an object |
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Plastic deformation |
An irreversible change in the shape of an object |
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Breaking strength |
The value of stress at the point of fracture of a material |
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Polymeric material |
A material comprising of long-chain molecules, such as rubber, which may show large strains |
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Brittle |
Property of a material that does not show plastic deformation and deforms very little before breaking |
