# Using physics to make things work

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- Created by: luciadoran
- Created on: 19-03-14 18:03

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- Using physics to make things work
- Moments
- a moment is a turning force around a fixed point
- Pivot- the point around which the moment acts
- Load- the thing the moment is moving.
- Effort- the force applied to move it
- Affected by: increasing distance from pivot and increasing force

- Balancing moments
- Balance the force on each side of the pivot.
- Calculate the moment so that the anti-clockwise and clockwise moments are equal.
- Finding the mass of a beam
- Calculate moment from force to pivot.
- Work out where the centre of mass will be
- Divide the moment by (centre of mass minus distance from pivot).

- Pendulums
- Pendulums oscillate.
- Increasing the length of the pendulum increases the time period.
- Time period is how long it takes for the pendulum to complete one oscillation.

- Simple pendulum has: a mass (bob), and is suspended by string.
- Amplitude is the angle between the equilibrium and the position of the bob.

- Centripetal force
- A force which acts in a circular motion towards the centre of the circle.
- Not a force in it's own right as it is always caused by something else.
- Objects moving in a circle are accelerating because their velocity is changing all of the time.
- If the centripetal force stopped acting the object would continue moving at a tangent to the circle.
- Increasing: mass of the object, and speed of the object increases centripetal force needed for movement.
- Decreasing the radius of the circle increases the centripetal force needed.

- Centre of mass
- The point around which the mass of the object is thought to concentrate.
- Depends on the shape of an object
- A freely suspended object will come to rest with the centre of mass below the point of suspension.

- Hydraulics
- Uses the principle of pressure in liquids and that liquids can't be compressed.
- Used to move heavy loads whilst exerting low force.
- 1. Calculate the pressure on the slave piston using: pressure= force/ area.
- 2. Calculate the force exerted from the master piston using the same equation- remember pressure stays the same!

- Finding the centre of mass
- 1. stick a pin through the shape and secure in a clamp stand.
- 2. When it stops moving secure a plumb line from the same pin.
- 3. Mark the position of the plumb line on the object.
- 4. Repeat using a different point.
- 5. Centre of mass is where the lines marking the plumb line are.

- Pressure in liquids
- Pressure increases with depth
- Pressure is transmitted equally to all points in the liquid.

- Moments

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