Practicals

• How to measure mass

  1. Use a digital balance

  2. Place solid object on balance and record reading

  3. For liquid: place measuring cylinder on balance, record reading, pour in liquid, record new reading and subtract mass of cylinder
• How to measure volume

  1. For liquid: use measuring cylinder, pour liquid in and read scale

  2. For regular solid: measure width, length, height and multiply

  3. For irregular solid: place in water-filled measuring cylinder, note initial reading, put object in, note new reading, subtract initial from final to get volume
• Measuring the density of a rock

  1. Measure mass using digital balance, repeat and calculate mean

  2. Measure volume using measuring cylinder and water, repeat and calculate mean

  3. Calculate density using equation: density = mass / volume

  4. Include units in all calculations and answer
• You need to work carefully to make accurate and precise measurements of mass and volume in order to find an object's density
• You measure mass using a digital balance
• To measure the mass of a solid, place it on the balance and record the reading
• To measure the mass of a liquid: place a measuring cylinder on a digital balance, write down the reading, pour in the liquid, write down the new reading and subtract the mass of the cylinder
• You can measure the volume of a liquid using a measuring cylinder. Pour the liquid into the cylinder and read off the scale
• You can measure the volume of a regular solid, such as a cube or rectangular block, by measuring the width, length, and height, then multiplying the measurements together to find the volume
• For an irregularly shaped solid object, you can use a measuring cylinder to measure the volume: pour water into a cylinder large enough to hold the object, note the reading, put the object into the water and note the new reading, subtract the initial reading from the final reading to find the volume
• Measuring the density of a piece of rock

  1. Use a digital balance to measure the mass of the rock, repeat readings and calculate mean

  2. Use a measuring cylinder and water to measure the volume of the rock, repeat readings and calculate mean

  3. Calculate the density using the equation: density = mass / volume

  4. Include units in all stages of the calculation and answer
• How to measure the force and extension of a spring

  1. To measure force: attach a newtonmeter directly to the spring and read the force, or use the fact that a 100g mass has a weight of 1 N

  2. To measure extension: measure the length of the spring with no force, then measure the length with a force and subtract to calculate the extension
• Hazard: If the spring breaks, the end of it can fly up and cause injury
• Investigating the behaviour of a spring

  1. Take a retort stand, boss, and clamp

  2. Attach the spring to the clamp using one of the loops

  3. Measure the original length of the spring

  4. Place a 1 N weight on the spring

  5. Measure the length again, then record the extension

  6. Repeat with more weights

  7. Repeat measurements for each force value, calculate mean extension
• Hooke's Law


  The relationship between force and extension: force (N) = spring constant (N/m) x extension (m)
• Calculating a spring constant

  Calculate the gradient of a graph of force against extension using the initial linear section
• How to take measurements to find acceleration

  Use light gates connected to a datalogger to accurately measure speed at two different times, then calculate acceleration from the change in speed and time
• It is difficult to measure speed and time accurately using a stopwatch and metre ruler
• An object moving past a light gate reflects the beam of light as it passes in front of it
• Investigating acceleration using light gates

  1. Connect light gates to datalogger to record time for object to pass each gate

  2. Fix a card to a trolley, measure the card width

  3. Raise a ramp, place trolley on it and let it accelerate

  4. Take readings of time for card to pass each light gate

  5. Use card width and time to calculate two speeds

  6. Calculate acceleration from change in speed and time
• Measuring the wavelength, frequency and speed of water waves in a ripple tank

  1. Wavelength: place ruler in tank and measure, or use stroboscope to 'freeze' waves and measure

  2. Frequency: count waves passing a marker per second, or use vibrating bar and paper

  3. Speed: measure wavelength and frequency, then use speed = frequency x wavelength
• There will be large uncertainties in all measurements of water wave properties
• An alternative way to measure wave speed is to have one student draw a line following a wave peak as it moves, while the other times the movement over a distance