# Physics Definitions Mechanics

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- Created by: Emily Cooke
- Created on: 26-03-14 15:05

Acceleration

Rate of change with time of velocity vector. Magnitude given by gradient of graph of v against t

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Centripetal Force

Name of any force or resultant of individual forces that point towards centre of a circular path

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Centripetal Acceleration

Acceleration due to a changing velocity direction. Points towards centre of circular path =v²/r

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Displacement

Distance in a given direction from a fixed origin, is a vector

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Efficiency

Ratio of useful output work to input work

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Energy Conservation

Energy cannot be destroyed or created, it can be transformed from one form to another. The mechanical energy of a system stays the same in absence of frictional forces

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Equipotential Surface

Set of points that have same gravitational potential

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Escape Speed

Minimum speed an object must have at the surface of a planet so that it can move an infinite distance away (escape its field) =√2GM/r

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Gravitational Field Strength

Gravitational force experienced by a point particle of unit mass. The field strength due to spherical or point mass M is g=GM/r²

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Gravitational Potential

Work done in bringing a point particle of unit mass from infinity to a point in a gravitational field v=-GM/r (scalar)

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Gravitational Potential Energy Difference

Work must be done in order to raise mass m by a vertical distance h Eg=mgh

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Gravitational Potential Energy of 2 Point Masses

Work done in moving 2 point masses M and m, which are infinitely far apart initially until they are separated by a distance r. Eg=-GMm/r

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Hooke’s Law

The tension in a spring is proportional to its extension and opposite to it

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Impulse

The total change in the momentum of a system as a result of a force acting on it. Its magnitude is given by the area under a force versus time graph. (vector)

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Law of Gravitation

There is an attractive force between any 2 point masses, given by =G (m₁m₂)/r^2 , r is their separation. Directed along line joining masses.

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Momentum Conservation

If the net external force on a system is zero, the total momentum of the system stays the same

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Newton’s First Law

If the net external force on a system is zero, the system remains at rest or moves with constant velocity

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Newton’s Second Law

The net force on a body equals the rate of change of the body’s momentum. When the mass is constant this is F=ma

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Newton’s Third Law

If a body A exerts a force on body B, then body B will exert and equal and opposite force on body A

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Orbit

The path of an object when under the influence of just the force of gravitation

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Orbital Speed

The speed of a body in orbit v=√(GM/r)

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Power

The rate at which work is being performed P=W/t (scalar)

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Translational Equilibrium

The state of a system where the net external force is zero

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Velocity

The rate of change with time of the displacement vector. Gradient of a graph of displacement versus time (vector)

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Weight

The force of gravitation on a body. Refers to gravitational force on a small body due to a large body such as a planet

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Work (Mechanical)

The product of the force times the distance moved by its point of application in the direction of the force. It is given by the area under the graph of force versus distance (scalar)

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Work Done in Gravitational Field

Work done in moving a mass from one point to another in a gravitational field W=mV. Independent of path followed

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Work-Kinetic Energy Relation

The net work done on a body (sum of work done by individual forces) equals change in kinetic energy of the body

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## Other cards in this set

### Card 2

#### Front

Name of any force or resultant of individual forces that point towards centre of a circular path

#### Back

Centripetal Force

### Card 3

#### Front

Acceleration due to a changing velocity direction. Points towards centre of circular path =v²/r

#### Back

### Card 4

#### Front

Distance in a given direction from a fixed origin, is a vector

#### Back

### Card 5

#### Front

Ratio of useful output work to input work

#### Back

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