Pressure, Density and Moments Flashcards
What is a Hydrometer and how does it work?
A hydrometer is a device used to measure density. It sinks into a liquid and then floats, we can read density off the scale.
Density is?
Pressure is?
Mass per unit volume.
Force per unit area
simple formulas
Density= Mass/Volume
Pressure=Force/Area
Pressure=(Density)(acceleration due to gravity)(height) or p=pgh
(p1)(v1)=(p2)(v2) (pressure and volume)
moment= force x distance
Archimedes principle:
When an object is immersed in fluid, the upthrust (in Newtons) is equal to the weight (in Newtons) of the displaced fluid.
Law Of Flotation:
The weight of a floating object is equal to the weight of fluid it displaces.
Boyles Law
At a contact temperature, the volume of a fixed mass of gas is inversely proportional to its pressure
Experiment to verify Boyles Law
Apparatus: Pressure gauge,screw, graduated scale to read volume of gas, fixed mass of gas
Procedure:
- The tube is filled with air.
- Note the pressure of the gas from the pressure-gauge and the volume from the graduated scale.
- Turn the screw to decrease the volume and increase the pressure.
- Note the new readings and repeat to get about seven readings.
- Draw a graph of pressure against 1/volume. This should result in a straight line through the origin.
Conclusion: After plotting the graph we got a straight line through the origin, thus proving pressure is inversely proportional to volume.
Sources of Error:
- Wait a minute for temperature (and therefore volume) to stabilise alter each pressure change before you read the volume.
- Have your eye level with the pressure gauge when taking readings to avoid parallax error.
- Work in a room where the temperature remains constant throughout the experiment.
- Guage may not have been accurate
- There was 1cm
Experiment to verify Boyles Law
Apparatus: Pressure gauge,screw, graduated scale to read volume of gas, fixed mass of gas
Procedure:
- The tube is filled with air.
- Note the pressure of the gas from the pressure-gauge and the volume from the graduated scale.
- Turn the screw to decrease the volume and increase the pressure.
- Note the new readings and repeat to get about seven readings.
- Draw a graph of pressure against 1/volume. This should result in a straight line through the origin.
Conclusion: After plotting the graph we got a straight line through the origin, thus proving pressure is inversely proportional to volume.
Sources of Error:
- Wait a minute for temperature (and therefore volume) to stabilise alter each pressure change before you read the volume.
- Have your eye level with the pressure gauge when taking readings to avoid parallax error.
- Work in a room where the temperature remains constant throughout the experiment.
- Guage may not have been accurate
- There was 1cm
Experiment to verify Boyles Law
Apparatus: Pressure gauge,screw, graduated scale to read volume of gas, fixed mass of gas
Procedure:
- The tube is filled with air.
- Note the pressure of the gas from the pressure-gauge and the volume from the graduated scale.
- Turn the screw to decrease the volume and increase the pressure.
- Note the new readings and repeat to get about seven readings.
- Draw a graph of pressure against 1/volume. This should result in a straight line through the origin.
Conclusion: After plotting the graph we got a straight line through the origin, thus proving pressure is inversely proportional to volume.
Sources of Error:
- Wait a minute for temperature (and therefore volume) to stabilise alter each pressure change before you read the volume.
- Have your eye level with the pressure gauge when taking readings to avoid parallax error.
- Work in a room where the temperature remains constant throughout the experiment.
- Guage may not have been accurate
- There was 1cm of air in the syringe tube, which was separate from our measured volume.
A lever is…..
Any rigid object free to turn about a fixed point called a fulcrum.
Laws or equilibrium state…..
- The vector sum of the forces in any direction is zero
2. The sum of moments about any point is zero
Torque
Movement of a couple
A couple are…….
Two parallel forces with the same magnitude acting in opposite directions.
Experiment to investigate the Laws of Equilibrium for a set of Co- Planar Forces
Apparatus: Two newton balances, metre stick, weights, paperclips, electronic balance
PROCEDURE
1. Find and note the centre of gravity of the metre-stick by hanging it from a thread and adjusting the position of the
thread such that the metre-stick is horizontal.
2. Find and note the mass of the metre-stick by weighing it on an electronic-balance.
3. Set up the apparatus as shown and move the weights around until the stick is horizontal and in equilibrium (not
rotating). the newton-metres must be vertical.
4. Record the reading on each newton-metre and the positions on the metre stick of each weight, each newton-metre
Conclusion
Using our formula we are able to verify both laws, within experimental error.
SOURCES OF ERROR / PRECAUTIONS
- Ensure that the newton balances are vertical and the metre stick is horizontal when readings are taken.
- Avoid parallax error when reading the lengths and forces.
- Use large weights (i.e. multiples of 1N) to reduce percentage errors.
