Exam Improvements Flashcards
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Explain how the graph demonstrates Newtons third law during the collison of the 2 objects
Force = Δp/Δt, which is the same as the gradient of the graph. The graph shows lines A and B with gradients of equal magnitude but in opposite directions (positive and negative). This shows they experience equal and opposite forces, therefore demonstrating Newtons third law
The student plucks the wire in the middle to form a wave on the wire. How may the student have determined the fundamental frequency of the oscillating wire?
Use a slow motion camera to count the number of oscillations. Include a timer in the video so you can determine the time. Frequency = number of oscillations / time.
Explain thge variation of V with distance x without the wire BC
Without the wire, the resistive wire and the resistor are now in series, the EMF is shared across the 2 components. Therefore, as x increases, the resistance of the wire increases causing V to decrease as the resistor’s resistance is a lower proportion of the total resistance and resistance is directly propotional to
State the 2 conditions for an object to be in equilibrium:
- The resultant force on the object must equal 0 in any direction
- The resultant moment around any point on the object must equal 0
At D, the superposition of waves will occur. As both waves come from the same source (T) they will have the same frequency and the saem constant phase difference, therefore they are coherent. The superposition of 2 coherent waves is known as interference The resultant wave detected at D will be the result of this interference and the amplitude of teh wave will be the sum of the 2 component waves. As y increases/decreases, the path difference between the waves changes. This can lead to maximum and minimums forming. As there is a 180° phase change when the microwaves are reflected, minimums occur when the path difference is an integer multiple of the wavelength and maximums occur half a wavelength above or below the minimums. The path difference is found using pythagoras and they are:
* When y = 8.4, PD = 1,4
* When y = 11.9, PD = 2.8
* When y = 14.6, PD = 4.2
* When y = 17, PD = 5.6
Therefore the wavelength is 2.8cm
-20V
A mass and spring are attached to a mechanical vibrator, which can oscillate with variable frequency. The vibrator frequency is varied from 0 Hz to 2.5 Hz. The mass-spring system has a natural frequency of 1.4 Hz. A light disk is then attached to the mass to increase the damping. Sketch a graph to show the variation with vibrator frequency of the amplitude of the mass (label it graph K) and the mass and light disc (label it graph D)
A student throws a ball vertically upwards, which of the following shows a free body diagram for the ball immediately after it leaves the students hand?
C
The oscillations of a car suspension system are heavily damped by a piston containing a high viscosity fluid. Explain why using oil of high viscosity will produce heavy damping
A high viscosity oil will mean a large resistive force is applied to the oscillations. When the piston moves, a large amount of work will be done against the oil. Therefore the energy of oscillations is quickly dissipated to the oil and therefore it produces heavy damping.
Explain the pattern of light observed when a mixture of blue and red light, from the same source, passes through a diffraction grating:
- Waves from different slits will undergo superposition on the surface behind the grating. Constructive interference will occur where the path difference is equal to nλ and the waves are in phase. Bright lines can be seen where constructive interference occurs
- The central maximum is due to a mixture of red and blue light
- λ = asin(θ)/n, therefore the spacing between maxima is larger for greater wavelengths. Therefore, maxima of blue light are closer together than maxima of red light as blue light has a shorter wavelength than red light.
Explain in terms of forces between plates, why the energy stored increases as the separation between 2 plates in a capacitor increases:
Work must be done against attractive forces
The diagram shows the relative lengths and diameters of two copper wires. What is the ratio of the resistivity of wire Y to wire X?
1:1
A
This pattern is obtained from the Young’s double-slit experiment. Explain how the part of the pattern labelled B is formed
Waves arrive in phase at B with a phase difference of 4π/720°. They also have a path difference of a whole number multiple of the wavelength, path difference = 2λ. Therefore, constructive interference occurs
Describe the apparatus required to produce this electron diffraction pattern
Evacuated tube, electron gun, graphite diffraction grating,
Draw the circuit to investigate a capacitor discharging and charging
Either of:
The plane of the search coil is rotated so it makes an angle with the central axis of the solenoid, what instrument can be used to determine the maximum induced electromotive force across the ends of the search coil?
a.c. voltmeter
