Out into Space

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  • Created by: helena
  • Created on: 26-05-13 18:17

Circular Motion

When an object is moving in a circular path its velocity is always at right angles to the radius

Centripetal Force pulls the object in a circular path
Therefore F is always at right angles to V

Two objects at different distances from the centre that have the same Angular Velocity will complete the same number of revolutions in a given time, but have different speeds
Angular Velocity = ω = 2π/t

v = ω*r

Time period = T = 2π/ω

f = 1/T = ω/2π

The acceleration of an object moving in a circle is called Centripetal Acceleration

a = v^2/r

a = ω^2 * r

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Kepler's Law's

A planet moves in an ellipse with the sun at one focus

The line from the sun to the planet sweeps out equal areas in equal times

The speed of the planet in orbit increases as it gets nearer the Sun

(orbit time)^2 is propotional to (orbit radius)^3

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Gravitational Potential

1/2*mv^2 = mgΔh

gravitational potential = Vgrav

Vgrav = gΔh

units = J per kg

The amount of potential energy depends on

  • mass of the object
  • mass of the planet
  • distance between them

This leads to the equation

Vgrav = -GMm/r

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Gravitational Field

Affects anything with mass

always attractive

pulls towards centre of the earth

g= F/m where

  • F= force and 
  • g=acceleration due to gravity

F = GM1M2/r^2

Force is proportional to each of the masses

The inverse square law: F is proportional to the square of the distances apart

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Conservation of Momentum

momentum = ρ (rho)

ρ = mv

Units = kgms^-1

A collision in which all the kinetic energy is conserved is considered elastic

Newtons second Law: F = mv/t

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