Download September 2002 - GF Abela Junior College

UNIVERSITY OF MALTA
G.F.ABELA JUNIOR COLLEGE
FIRST YEAR
END-OF-YEAR TEST
Resit Session
Subject: Physics
Date: 4th September 2002
Level: Advanced
Time: 09.00 – 12.00hrs
Directions to Candidates
You are requested to show all your working and write the units
where necessary.
Answer ALL questions from Section A.
Answer any TWO questions from Section B.
Answer any TWO questions from Section C.
Wherever necessary assume g = 10ms-2.
Section A
Attempt ALL eight questions in this section. Each question carries 5 marks. This
section carries 40% of the total mark for this paper.
1a. State Newton’s second law of motion.
(1)
b. A compressed air gun shoots ten ping-pong balls a second. They travel horizontally
at 14ms-1 and have a mass of 8.0g each. They rebound from a vertical wall following
an elastic collision. Calculate the force on the wall.
(4)
2. The graph below is a stress-strain graph of a material that obeys Hooke’s law.
Stress/MPa
200
100
0.5
1.0
Strain/x 10-3
(a) What is the Young’s modulus of the material whose stress-strain graph is
shown.
(2)
(b) Show that the area under this graph is equal to the work done per unit
volume of the material. (No numerical calculation is required)
(3)
3. A pendulum bob of mass 2kg is attached to one end of a string. The bob moves in a
horizontal circle in such a way that the string is inclined at 30° to the vertical.
Calculate:
(a)
the tension in the string,
(2)
(b)
the centripetal force acting on the bob.
(3)
4a. After passing through a grating of slits, each separated by a distance d, the waves
of wavelength λ reinforce if their path difference is a whole number n of
wavelengths. Use a diagram to derive the diffraction grating formula
dsinθ
θ = nλ
λ
(3)
b. Calculate the angular position of the second order maximum created when
monochromatic light of wavelength 700nm passes through a diffraction grating of
spacing 3.5 µm.
(2)
5. The graph in figure shows the velocity of a skydiver as she jumps from an
aeroplane.
(a) State what type of motion results in the region AB
(b) What do you think happens at X?
(c) Why is the velocity at D lower than at C?
(2)
(1)
(2)
6. How far from a converging lens of focal length 45cm must an object be placed
if the image is to be three times as large as the object and
(a) real,
(2)
(b) virtual?
(3)
7. The diagram shows a lorry of mass 45 000kg crossing a bridge. The span from
A and B is 32m.
A
B
(a) When the lorry is at the centre of the bridge, what is the increase in the
reaction of the bridge supports A and B on the bridge structure?
(2)
(b) Where on the bridge will the lorry be when the extra reaction of the bridge
support at A is 120 000N?
(3)
8. A grooved disc of radius 0.15m and moment of inertia 0.45kgm2 is mounted on
a horizontal axle using frictionless bearings. A cord is used to exert a tangential
force of 20N at the edge of the disc for a time of 5s.
groove on
edge
of disc
cord
0.15m
20N
axle
Assuming it starts from rest, calculate:
(a) the angular acceleration of the disc while the force is applied,
(b) the maximum angular velocity of the disc.
Section B
Attempt TWO questions in this section. Each question carries 15marks. This
section carries 30% of the total mark of this paper.
9. Figure shows part of a standing wave on a string at times t = 0ms and t = 10ms,
during which time the string has moved from the first position to the second.
(a) What is the period of the oscillation?
(3)
(b) Sketch on your booklet, the appearance of the string at 5ms.
(2)
(c) By referring to the frequency and the amplitude of point X, describe its motion. (2)
(d) What is the phase difference between points X and Y?
(2)
(e) Explain using the principle of superposition, why point Z is stationary.
(3)
(f) Calculate the speed of transverse waves on this string.
(3)
10. You are required to perform a two-slit experiment to determine the wavelength of
light from a given monochromatic source.
(a) Describe, with the aid of a well-labelled diagram, the apparatus you would use
for such a measurement.
(3)
(b) Assuming that red light is used, describe in detail the fringe pattern you would
expect to observe.
(3)
(c) Explain using the wave theory of light how the fringe pattern results.
(4)
(d) Describe how the required measurements are made, and show how the
wavelength would be calculated.
(5)
11. The diagram shows some of the energy levels of an electron in a mercury atom.
Level Q represents the lowest possible energy level.
(a)Explain why a line spectrum results from an atom with such energy levels.
(3)
(b) Calculate the energy change in joules when the electron moves from level P to
level Q and determine the wavelength of the spectral line associated with this
transition.
(5)
(c)Explain what is likely to happen if a moving electron of energy 7.0eV collides with
an isolated mercury atom in the ground state.
(4)
(d)Explain what is likely to happen if a photon, also of energy 7.0eV were to be
incident on the atom.
(3)
Planck’s constant = 6.6 x 10-34 Js,
speed of light = 3.0 x 108m/s,
charge on an electron = 1.6 x 10 -19 C
Section C
Attempt TWO questions in this section. Each question carries 15marks. This
section carries 30% of the total mark of this paper.
12a. A capacitor is marked 8µ
µF, 30V. What do the markings on the capacitor
indicate?
(4)
b. An 8µF capacitor is charged to 30V and then removed from the battery. It is next
connected across an uncharged 4µF capacitor.
(i) Calculate the charge on the 8µF capacitor after it has been charged?
(2)
(ii) Calculate also the capacitance of the combination of capacitors.
(2)
(iii)What is the new potential difference across the 8µF capacitor?
(4)
(iv) What is the charge on the 8µF capacitor?
(2)
(v) How much charge is transferred to the 4µF capacitor?
(1)
13. The figure shows a region of space near the earth’s surface. The earth’s radius is
6.4 x 106 m and gravitational potential at infinity is zero.
10 x 106m
10 x 106m
(a) Define gravitational potential at a point in a gravitational field.
(2)
(b) Calculate the gravitational potential at A and at B.
(4)
(c) A spacecraft of mass 2200kg moves from A to B. What is the change in
potential energy of the spacecraft?
(2)
(d) As the spacecraft falls towards the earth, it loses gravitational potential energy.
What becomes of the lost potential energy when the spacecraft is falling:
(i) freely, towards the earth well away from the earth’s atmosphere,
(2)
(ii) through the earth’s atmosphere at constant speed.
(2)
(e) As the spacecraft returns to Earth, it passes through B with a speed of 4km/s.
With what speed will it be moving when it passes through A? What
assumption have you made in this case?
(3)
(G = 6.67 x 10-11Nm2kg-2, Mass of earth = 6 x 1O 24kg)
14(a). Define the electric field strength at a point in an electric field and state its units
(2)
(b) A large, hollow, metal sphere is charged positively and insulated from its
surroundings. Sketch graphs of (i) the electric field strength and (ii) the electric
potential, from the centre of the sphere to a distance of several radii.
(4)
c) A water molecule consists of one oxygen atom and two hydrogen atoms. A student
suggests that the oxygen atom acts as a point charge of magnitude –1.1 x 10-19 C and
that each hydrogen atom acts as a point charge of magnitude +0.55 x 10-19C. The
oxygen atom is separated from each hydrogen atom by a distance of 1.0 x 10-10m, and
the arrangement of the atom is as shown in figure.
1.0 x 10-10m
1.0 x 10-10m
108°°
Assuming that the student’s model is correct,
(i)
(ii)
calculate the magnitude of the force exerted on the oxygen atom by one of
the
draw a diagram showing each of the forces acting on the oxygen atom due
to the hydrogen atoms and determine the magnitude and direction of the
resultant of these forces
(3,3)
(Permittivity of free space, εo = 8.8 x 10–10Fm-1)