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32 Cards in this Set
- Front
- Back
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Scalar quantities
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have magnitude only (i.e. no direction). e.g. distance, speed, mass, time, energy, work.
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Vector quantities:
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have magnitude & direction. e.g. displacement, velocity, acceleration, force, momentum.
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Distance (s or x)
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total distance travelled in metres. (Scalar quantity - no direction needed.)
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Displacement (s):
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“distance travelled in a specified direction from a given starting point”
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Resolving a vector:
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You need to be able to resolve a vector into two components at right angles by using either a scale drawing or by calculation using sin & cos
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Combining vectors:
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You need to be able to combine two vectors by calculation if they are at right angles to each other (using Pythagoras theorem and tan) or by scale drawing if there are more than two vectors and they are not at right angles to each other.
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Speed (v):
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“Rate of change of distance” in m s-1. (Scalar)
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Velocity (v):
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“Rate of change of displacement” measured in m s-1. (Vector)
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Acceleration (a):
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“Rate of change of velocity” in m s-2.
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Mass:
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The mass of an object is a measurement of the amount of matter it contains. The mass of any object (in kg) remains the same wherever it is in the Universe
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Weight:
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The weight of an object (on the Earth) is the gravitational force exerted by the Earth on the object. The weight of the object will change depending on where it is in the Universe.
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Gravitational field strength (g):
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This is the gravitational force exerted on a mass of 1 kg. It is defined by the equation g = F / m and has a value of 9.81 N kg 1 on the surface of the Earth.
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Displacement-time graph (s on y-axis, t on x-axis):
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gradient = velocity.
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Velocity-time graph (v on y-axis, t on x-axis):
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gradient = acceleration, area under = displacement.
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Acceleration-time graph (a on y-axis, t on x-axis):
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area under graph = change in velocity
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Momentum:
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Defined as mass × velocity. (Units: kg m s-1)
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Newton’s 1st law:
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“An object will remain in a state of rest or continue to move with a constant velocity unless acted upon by a resultant external force.” F = 0 ∴ acceleration = 0
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Newton’s 2nd law:
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“The acceleration of a body of constant mass is proportional to the resultant force appliedto it and in the direction of the resultant force.” It is represent by the equation: F = m a.
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Newton’s 3rd law:
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“While body A exerts a force on body B, body B exerts an equal and opposite force on body A”
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Equilibrium:
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A body is in equilibrium if, when acted on by a number of forces, the resultant force is zero. (The forces can be said to be “balanced” but not equal)
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Principle of conservation of linear momentum
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“In any interaction between bodies, momentum remains constant provided no resultant external force acts.”
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Newton’s 2nd Law (in terms of momentum):
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“The resultant force exerted on a body is directly proportional to the rate of change of linear momentum.”
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Impulse:
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The change in momentum of a body caused by a resultant force (unit = Ns).
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Force-time graph:
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The area under a F-t graph is equal to the impulse (change in momentum)
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Moment of a force:
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The product of the force and the perpendicular distance between the axis of rotation and the line of action of the force.
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The Principle of Moments:
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“If a system is in equilibrium, the sum of the clockwise moments must equal the sum of the anticlockwise moments about any point.”
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Principle of conservation of energy:
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“Energy cannot be created or destroyed, it can only be transferred from one form to another”
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Power (P):
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“the rate that work is done” (or the rate at which energy is transferred.) Unit is Js-1 (or W. Watt).
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Work or Work done (W):
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Work is done on an object when a force is used to transfer energy to it.
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