PHYA2 Revision minutes. 72 marks. Page 1 of 20

Transcription

1 PHYA Revision 1 73 minutes 7 marks Page 1 of 0

2 Q1. An aerial system consists of a horizontal copper wire of length 38 m supported between two masts, as shown in the figure below. The wire transmits electromagnetic waves when an alternating potential is applied to it at one end. (a) The wavelength of the radiation transmitted from the wire is twice the length of the copper wire. Calculate the frequency of the transmitted radiation (1) (b) The ends of the copper wire are fixed to masts of height 1.0 m. The masts are held in a vertical position by cables, labelled P and Q, as shown in the figure above. (i) P has a length of 14.0 m and the tension in it is 110 N. Calculate the tension in the copper wire. (ii) The copper wire has a diameter of 4.0 mm. Calculate the stress in the copper wire. Page of 0

3 (iii) Discuss whether the wire is in danger of breaking if it is stretched further due to movement of the top of the masts in strong winds. breaking stress of copper = Pa (7) (Total 8 marks) Q. (a) A laser emits monochromatic light. Explain the meaning of the term monochromatic light (1) Page 3 of 0

4 (b) The diagram below shows a laser emitting blue light directed at a single slit, where the slit width is greater than the wavelength of the light. The intensity graph for the diffracted blue light is shown. The laser is replaced by a laser emitting red light. On the axes shown in the diagram above sketch the intensity graph for a laser emitting red light. (c) State and explain one precaution that should be taken when using laser light Page 4 of 0

5 (d) The red laser light is replaced by a non-laser source emitting white light. Describe how the appearance of the pattern would change (3) (Total 8 marks) Q3. A supertanker of mass kg, cruising at an initial speed of 4.5 m s 1, takes one hour to come to rest. (a) Assuming that the force slowing the tanker down is constant, calculate (i) the deceleration of the tanker, (ii) the distance travelled by the tanker while slowing to a stop. (4) (b) Sketch, using the axes below, a distance-time graph representing the motion of the tanker until it stops. Page 5 of 0

6 (c) Explain the shape of the graph you have sketched in part (b) (Total 8 marks) Q4. The diagram below shows three transparent glass blocks A, B and C joined together. Each glass block has a different refractive index. (a) State the two conditions necessary for a light ray to undergo total internal reflection at the boundary between two transparent media. condition condition Page 6 of 0

7 (b) Calculate the speed of light in glass A. refractive index of glass A = 1.80 speed of light... ms 1 (c) Show that angle θ is about 30 o. (d) The refractive index of glass C is Calculate the critical angle between glass A and glass C. critical angle... degrees (e) (i) State and explain what happens to the light ray when it reaches the boundary between glass A and glass C (ii) On the diagram above continue the path of the light ray after it strikes the boundary between glass A and glass C. (1) (Total 11 marks) Page 7 of 0

8 Q5. Earthquakes produce transverse and longitudinal seismic waves that travel through rock. The diagram below shows the displacement of the particles of rock at a given instant, for different positions along a transverse wave. (a) State the phase difference between (i) points A and B on the wave... (ii) points A and C on the wave... (b) Describe the motion of the rock particle at point B during the passage of the next complete cycle (c) A scientist detects a seismic wave that is polarised. State and explain what the scientist can deduce from this information (d) The frequency of the seismic wave is measured to be 6.0 Hz. (i) Define the frequency of a progressive wave..... (1) Page 8 of 0

9 (ii) Calculate the wavelength of the wave if its speed is m s 1. wavelength... m (Total 9 marks) Q6. The figure below shows an apparatus used to locate the centre of gravity of a non-uniform metal rod. The rod is supported horizontally by two wires, P and Q and is in equilibrium. (a) State two conditions that must be satisfied for the rod to be in equilibrium (b) Wire Q is attached to a newtonmeter so that the force the wire exerts on the rod can be measured. The reading on the newtonmeter is.0 N and the weight of the rod is 5.0 N. Calculate (i) the force that wire P exerts on the rod, Page 9 of 0

10 (ii) the distance d. (3) (Total 5 marks) Q7. The figure below shows a skateboarder descending a ramp. The skateboarder starts from rest at the top of the ramp at A and leaves the ramp at B horizontally with a velocity v. (a) State the energy changes that take place as the skateboarder moves from A to B (b) In going from A to B the skateboarder s centre of gravity descends a vertical height of 1.5 m. Calculate the horizontal velocity, v, stating an assumption that you make (3) Page 10 of 0

11 (c) Explain why the acceleration decreases as the skateboarder moves from A to B (d) After leaving the ramp at B the skateboarder lands on the ground at C 0.4 s later. Calculate for the skateboarder (i) the horizontal distance travelled between B and C, (ii) the vertical component of the velocity immediately before impact at C, (iii) the magnitude of the resultant velocity immediately before impact at C. (5) (Total 1 marks) Q8. (a) (i) Describe the behaviour of a wire that obeys Hooke s law. (ii) Explain what is meant by the elastic limit of the wire. Page 11 of 0

12 (iii) Define the Young modulus of a material and state the unit in which it is measured. (5) (b) A student is required to carry out an experiment and draw a suitable graph in order to obtain a value for the Young modulus of a material in the form of a wire. A long, uniform wire is suspended vertically and a weight, sufficient to make the wire taut, is fixed to the free end. The student increases the load gradually by adding known weights. As each weight is added, the extension of the wire is measured accurately. (i) What other quantities must be measured before the value of the Young modulus can be obtained? (ii) Explain how the student may obtain a value of the Young modulus. (iii) How would a value for the elastic energy stored in the wire be found from the results? (6) (Total 11 marks) Page 1 of 0

13 M1. (a) λ(= 38) = 76(m) MHz (1) 1 (b) (i) angle between cable and horizontal = (1) T= 110 cos59 = 57N (56.7N) (1) (allow C.E. for value of angle) (ii) cross-sectional area (= Π( ) ) = (m ) (1) ( (m )) stress (1) = Pa (1) ( Pa) (use of 56.7 and 1.6 gives Pa) (allow C.E. for values of T and area) (iii) breaking stress is 65 stress copper is ductile copper wire could extend much more before breaking because of plastic deformation extension to breaking point unlikely any three (1)(1)(1) 7 [8] M. (a) single frequency (or wavelength or photon energy) not single colour accept very narrow band of frequencies 1 (b) subsidiary maxima (centre of) peaks further away from centre For second mark: One square tolerance horizontally. One whole subsid max seen on either side. subsidiary maxima peaks further away from centre AND central maximum twice width of subsidiaries AND symmetrical Central higher than subsid and subsid same height + / squares. Minima on the x axis + / 1 square. Must see 1 whole subsidiary for second mark Page 13 of 0

14 (c) ONE FROM: don't shine towards a person avoid (accidental) reflections wear laser safety goggles 'laser on' warning light outside room Stand behind laser other sensible suggestion allow green goggles for red laser, high intensity goggles, etc. not goggles, sunglasses eye / skin damage could occur (d) 3 from 4 central white (fringe) each / every / all subsidiary maxima are composed of a spectrum (clearly stated or implied) each / every / all subsidiary maxima are composed of a spectrum (clearly stated or implied) AND (subsidiary maxima) have violet (allow blue) nearest central maximum OR red furthest from centre Fringe spacing less / maxima are wider / dark fringes are smaller (or not present) allow white in middle For second mark do not allow there are colours or there is a spectrum on their own Allow rainbow pattern instead of spectrum but not a rainbow Allow rainbow pattern instead of spectrum but not a rainbow If they get the first, the second and third are easier to award Allow full credit for annotated sketch 3 [8] M3. (a) (i) (use of gives) (1) = ms (1) (ii) (use of v = u +as gives) 0= s (1) (1) 4 (b) increasing curve (1) correct curve (1) 1 Page 14 of 0

15 (c) gradient (slope) of graph represents speed (1) hence graph has decreasing gradient (1) [8] M4. (a) n 1 > n Allow correct reference to optical density (incident) angle > critical angle (allow θ c not c ) OR critical angle must be exceeded Allow n A > n B Do not allow: angle passes the critical angle (b) For second mark, don t allow Allow or Allow (= ) = (ms 1 ) (c) sin7 = 1.80sin θ Correct answer on its own gets both marks θ = = 31.9 correct answer >= sf seen Do not allow 31 for second mark Allow (d) 1.80 sin θ c =1.40 OR θ c = = 51.1 (accept 51) Correct answer on its own gets both marks Don t accept 50 by itself Page 15 of 0

16 OR = (e) (i) + their (c) ( = 53.9) 53.9 > (51.1) critical angle If c + < d then TIR expected If c + > d then REFRACTION expected OR c + < their d (θ c ) ecf from (c) and (d) angle less than critical angle Allow max 1 for TIR because angle > critical angle only if their d > c + (ii) TIR angle correct ecf from e(i) for refraction answer Tolerance: horizontal line from normal on the right / horizontal line from top of lower arrow. If ei not answered then ecf (d). If ei and d not answered then ecf c 1 [11] M5. (a) (i) π / (radians) or 90 (degrees) No path differences Penalise contradictions No fractions of a cycle 1 (ii) 3π / (rad) or 70 (degrees) No path differences Penalise contradictions No fractions of a cycle 1 (b) (oscillation or motion) perpendicular to direction of wave (travel / velocity / energy transfer) (oscillates from equilibrium to maximum positive displacement, back to equilibrium, then to max negative displacement) and back to equilibrium / starting position / rest position do not allow up and down for first mark allow up and down, or down then up, side to side, rise and fall in place of oscillates Allow rest position, starting position, middle, centre line ref to nodes / antinodes not allowed for nd mark (c) (the wave is) transverse OR not longitudinal accept it is an S wave or secondary wave only transverse can be polarised OR longitudinal waves cannot be polarised OR oscillations are in one plane Page 16 of 0

17 (d) (i) number of waves / complete cycles / wavelengths (passing a point / produced) per second or unit time allow: (number of) oscillations / vibrations / cycles per second allow f=1 / T only if T is correctly defined do not allow references to f=c / λ 1 (ii) ( v = f / λ λ = v / f = ) / 6.0 = 750 (m) correct answer only gets marks [9] M6. (a) resultant force zero (1) resultant torque about any point zero (1) (b) (i) force due to wire P = = 3.0 N (1) (ii) (moments give) 5.0 d = (1) d= 0.36 m (1) 3 [5] M7. (a) potential energy to kinetic energy (1) mention of thermal energy and friction (1) (b) (use of ½ mv = mgh gives) ½ v h = (1) v h = 5.4ms 1 (1) (assumption) energy converted to thermal energy is negligible (1) (c) component of weight down the slope causes acceleration (1) this component decreases as skateboard moves further down the slope (1) air resistance/friction increases (with speed) (1) 3 Page 17 of 0

18 (d) (i) distance (= ) =.3m (1) (.7m) (allow C.E. for value of v h from (b)) (ii) v v = (1) 1 (1) = 4.1(l) m s (iii) v = (1) v = 6.8 m s 1 (1) (6.78 m s 1 ) (allow C.E. for value of v h from (b)) 5 [1] M8. (a) (i) the extension produced (by a force) in a wire is directly proportional to the force applied (1) applies up to the limit of proportionality (1) (ii) elastic limit: the maximum amount that a material can be stretched (by a force) and still return to its original length (when the force is removed) (1) [or correct use of permanent deformation] (iii) the Young modulus: ratio of tensile stress to tensile strain (1) unit: Pa or Nm (1) 5 (b) (i) length of wire (1) diameter (of wire) (1) (ii) graph of force vs extension (1) reference to gradient (1) gradient = (1) [or graph of stress vs strain, with both defined reference to gradient gradient = E] area under the line of F vs ΔL (1) [or energy per unit volume = area under graph of stress vs strain] 6 [11] Page 18 of 0

19 N1. Question source: Legacy Spec A June 006 Unit 10 Question 8 Description: Horizontal copper aerial; breaking stress Marks: 8 Mathematical requirements: Decimal and standard form Calculator functions Manipulate equations Substitution Solve equations Circumference; area; volume Sin x; cos x; tan x Topic: Elastic properties of solids Type: Structured quantitative Specification:..1 Bulk properties of solids.3.1 Progressive waves N. Specification 7408 Question source: June 013 Unit Question 7 Description: Diffraction at single slit Marks: 8 Maths requirements: Translate information between forms Maths demand: Topic: Oscillation and waves Type: State/explain/describe Specification: Diffraction Specification 450 Question source: June 013 Unit Question 7 Description: Single slit diffraction using a laser Marks: 8 Maths requirements: Translate information Topic: Oscillation and waves Type: State/explain/describe Specification:.3.6 Diffraction N3. Question source: Legacy Spec A June 006 Unit Question 6 Description: Supertanker coming to rest Marks: 8 Mathematical requirements: Decimal and standard form Calculator functions Manipulate equations Substitution Solve equations Translate information Tangent + rate of change Topic: Mechanics Type: Structured quantitative Specification:.1.3 Motion along a straight line N4. Question source: June 013 Unit Question 5 Description: Light travelling though glass block Marks: 11 Mathematical requirements: Substitution Solve equations Pythagoras; angle sum of triangle Sin x; cos x; tan x Degrees and radians Topic: Oscillation and waves Type: Structured quantitative Specification:.3.3 Refraction at a plane surface Page 19 of 0

20 N5. Specification 7408 Question source: June 013 Unit Question 6 Description: Transverse seismic wave Marks: 9 Maths requirements: Decimal + standard form Substitution Translate information between forms Maths demand: 1 Topic: Oscillation and waves Type: State/explain/numerical Specification: Progressive waves Longitudinal + transverse waves Specification 450 Question source: June 013 Unit Question 6 Description: Transverse seismic wave Marks: 9 Maths requirements: Decimal and standard form Translate information Topic: Oscillation and waves Type: State/explain/numerical Specification:.3.1 Progressive waves.3. Longitudinal and transverse N6. Question source: Legacy Spec A June 006 Unit Question 3 Description: Suspended rod Marks: 5 Mathematical requirements: Substitution Solve equations Topic: Mechanics Type: State/explain/numerical Specification:.1. Moments N7. Question source: Legacy Spec A June 006 Unit Question Description: Skateboarder; ramp; projectile motion Marks: 1 Mathematical requirements: Calculator functions Substitution Solve equations Pythagoras; angle sum of triangle Topic: Mechanics Type: State/explain/numerical Specification:.1.4 Projectile motion.1.7 Conservation of energy N8. Question source: Legacy Spec A June 006 Unit 3 Question 5 Description: Hooke's Law; elastic limit; Young modulus Marks: 11 Mathematical requirements: None Topic: Elastic properties of solids Type: State/explain/describe Specification:..1 Bulk properties of solids.. The Young modulus Page 0 of 0