Physics Practical Summaries

    This is old - I made these notes so I could prepare for the mock.
    Please use the four separate pages for Core and Advanced Physics instead.

Core Physics I

    CP 1 Determining the acceleration of a freely falling object:

    • Drop a flat object through two light gates. Vary the distance between them
    • Plot distance against time squared. Multiply the gradient by 2 to get the acceleration due to gravity

    CP 2 Determining the resistivity of a wire:

    • Measure the diameter in several places with a micrometer and find the mean
    • Measure the current and pd for several different lengths
    • Plot resistance against length (should be through origin)
    • Multiply the gradient by the cross sectional area (A=πr2A = \pi r^2) to get the resistivity

    CP 3 Finding internal resistance and emf:

    • Connect a fixed resistor and a cell (or a potato). Add an ammeter in series and voltmeter in parallel
    • Take readings with different resistors
    • Plot pd against current. It should have a negative gradient
    • The yy-intercept is the emf
    • The negative of the gradient is the internal resistance

    Core Physics II

      CP 4 Finding the viscosity of a liquid:

      • Drop a ball of known diameter into a cylinder of liquid. Measure the time it takes to fall a marked distance
      • Stokes' law (F=6πηrvF = 6\,\pi\,\eta\,r\,v) can now be used to calculate the viscosity of the liquid
      • Multiple balls of different diameters could be used to improve the results as there will be a large uncertainty in time measurements

      CP 5 Finding the Young modulus of a material:

      • Clamp a long copper wire inside some wooden blocks. The other end should go over a pulley attached to a mass
      • Measure its diameter in several places and calculate the mean
      • Attack a paper marker to the wire, over a ruler
      • Record the distance between the marker and clamped end. This is ll
      • Increase the weight and record the mass and difference between the base length and current one
      • Calculate stress and strain
      • Plot a stress-strain graph through the origin
      • The Young Modulus is the gradient

      CP 6 Calculating the speed of sound in air:

      • Connect a microphone and signal generator to an oscilloscope as inputs
      • Connect a speaker to the same signal generator
      • Move the microphone until the waves are in phase. Record this distance. Keep doing this, moving the microphone further away
      • Find the mean of the distances between each pair of readings. Multiply this by the frequency (from the signal generator, or the oscilloscope for greater accuracy)

      CP 7 The effects of length/tension/mass per unit length on a vibrating string:

      • Use a signal generator and vibration generator to vibrate a string connected to a mass through a pulley
      • You can modify the length, tension or mass per unit length. Then adjust the frequency until one wavelength of a standing wave is formed
      • Plot a graph of 1f\frac{1}{f} against λ\lambda. The gradient is the mass per unit length
      • Use the equation f=12l×Tμf = \frac{1}{2l} \times \sqrt{\frac{T}{\mu}}

      CP 8 Using a diffraction grating to calculate the wavelength of a laser:

      • Put a diffraction grating over a laser. Clamp this a set distance from a wall
      • Measure the distance between the zero order (centre) and first order dots (each side of the central one). Take the mean between these two readings
      • θ=tan1(\theta = tan^{-1}(distance between dots ÷\div distance from laser to wall))
      • λ=\lambda = distance from laser to wall ×sinθ\times sin\,\theta

      Advanced Physics I

        CP 9 Proving Δp=FΔt\Delta p = F\Delta t:

        • Create a surface for a trolley. Compensate for friction. (or use an air track)
        • Set up two light gates. Connect the trolley to a hanging mass with a pulley and string. msystem=m_{\mathrm{system}} = trolley mass ++ hanging mass
        • Release the trolley from the top. Use the change in velocity from the light gates in Δpsystem=msystemΔv\Delta p_{\mathrm{system}} = m_{\mathrm{system}} \Delta v
        • Divide this by the time between the two light gates (Δt\Delta t)
        • Calculate total force with F=MgF = Mg (MM is the hanging mass)
        • Do repeats, and vary the hanging mass
        • Plot FF against Δpsystem\Delta p_{\mathrm{system}}
        • If it's a straight line, Δp=FΔt\Delta p = F\Delta t

        CP 10 Analysing collisions between small spheres:

        • Roll a sphere into another, whilst recording with a video camera. Put rulers on the table in view of the camera
        • Use software to find the distance travelled each frame, in xx and in yy. Multiply each by the framerate to get the velocity in that direction
        • The total momentum before and after the collision should be equal

        CP 11 Analysing capacitor charging and discharging:

        • Connect a CRO to a capacitor-resistor circuit (in parallel)
        • Set the timebase to 0 so there's a dot rather than a wave
        • Use a timer (with lap function) to record the time it takes to fall/rise one division for an entire charge/discharge
        • Plot a V-t graph
        • (or use a data logger, ammeter and voltmeter)