Dept. of Education and Science – Revised Sample Paper
Question 5.
15N
Attempt any five of the following parts
(a)
600
A force of 15 N acts on a box as shown. What is the horizontal component of the force?
Fh = 15 Cos 600 = 7.5 N
(b)
State Hooke’s Law
The restoring force of an ideal spring is
F = -kx
where k is the spring constant and x is the displacement of the spring from its unstrained
length. The minus sign indicates that the restoring force always points in a direction opposite
to the displacement of the spring.
(c)
100 litres of carbon dioxide gas at an atmospheric pressure of 1 x 105 Pa was pumped into a
gas cylinder of volume 0.5 litres. What is the pressure in the gas cylinder?
P1 V1
(1 x 105 )(100)
P2
(d)
=
=
=
=
P2 V2
( P2 )(0.5)
(1 x 105 )(100) /0.5
2 x 107 Pa
What is meant by the U-value of a structure?
It is the rate of heat flow through unit area of the structure, per unit temperature difference
across the structure. The units are W m-2 K-1 .
(e)
What is the shortest wavelength of sound that can be heard in air by a person given that the
frequency response of the ear ranges from 20Hz to 20 kHz? (Speed of sound in air = 340ms -1 ).
The highest frequency would have the shortest wavelength.
v = f λ => λ = v/f = 340/20,000 = 1.7 cm
(f)
A tin whistle, which acts like an open pipe, has a fundamental frequency of 256 Hz. What is
the frequency of the second harmonic?
The longitudinal standing wave for the second harmonic is half the wavelength of the
fundamental => the frequency of the second harmonic is double. Ans: 512 Hz.
(Remember, all multiples of the fundamental are present in open tubes)
(g)
A capacitor is marked 100 µF. What is the energy stored in the capacitor when it is connected
to a 6 V d.c. supply?
E = ½CV2 = ½ (100 x10-6 ) (6)2 = 1.8 x 10-3 J
(h)
The peak value of an a.c. supply is 15 V, calculate its rms value.
Vrms
=
Vmax
2
=
15
2
= 10 .6V
 Chris Garvey 2002
(i)
Give two properties of x-rays.
•
•
(j)
They cannot be deflected by electric or magnetic fields
They can cause photoelectric emission in metals.
Distinguish between leptons and baryons
Leptons are particles that interact by means of the weak nuclear force and they are elementary
particles whereas baryons interact by means of the strong nuclear force and the weak nuclear
force and they are made up of various combinations of quarks and hence they are not
elementary.
What is the principle on which a loudspeaker is based?
A conductor carrying a current and situated in a magnetic field experiences a force.
 Chris Garvey 2002