- String- Inextensible and has no mass
- Particle- Has no size but does have mass
- Rigid Body- Has size but does not change shape
- Smooth- Has no friction
- Rough- Has friction
- Light- Has no mass
- Inelastic/Inextensible- Does not stretch
Kinemetics in one dimension
- In a Displacement-time graph, the velocity is calculated by working out the gradient (y/x =velocity)
- Velocity-time graphs have a gradient equivalent to acceleration. (y/x=accelration)
- Area under a Velocity-time graph= Distance travelled
- s=ut+0.5at^2 or s=vt-0.5at^2
- Where s=displacement, u=initial velocity, v=final velocity, a=acceleration, t=time.
- Formulae only work when acceleration is constant
- Acceleration due to gravity(g)= 9.8 metres per second
Kinematics in two dimensions
- Positions, velocities and accelerations can be expressed in the form xi+yj
- Constant acceleration equations (shown above) can be used in two dimensions. Once in the i direction and once in the j direction. Adding both i and j together gives a vector.
- Magnitude and Direction of vectors can be calculated using trigonometry and pythagoras.
- Force is a vector quantity
- Resultant force=two or more forces added together using its perpendicular components.
- Particle is in equilibrium if resultant=0
- Weight= mass x acceleration due to gravity (W=mg)
- Frictional force between two surfaces in contact will act in a opposite direction to the…
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