WIT
HIGHER CERTIFICATE IN SCIENCE
HIGHER CERTIFICATE IN AGRICULTURAL
SCIENCE
BSc IN FOOR SCIENCE WITH BUSINESS
SEMESTER ONE
EXAMINATION:
INTRODUCTORY PHYSICS
YEAR 1
December 2008
EXAMINERS:
DURATION: 2 HOURS
Ms CATHERINE WALSH
Dr CORMAC O’RAIFEARTAIGH
Mr JAMES KELLY
INSTRUCTIONS TO CANDIDATES
1
2
3
ANSWER FOUR QUESTIONS
ALL QUESTIONS CARRY EQUAL MARKS
PHYSICAL CONSTANTS ON BACKPAGE
WATERFORD INSTITUTE OF TECHNOLOGY
Section A
Question One
(a) (i)
Define and state the S.I. unit of measurement for the following quantities
speed,
velocity
(ii) Explain the difference between a vector and a scalar quantity giving an
example of each.
(iii) Convert each of the following to correct S.I. units and use scientific notation.
23 g,
2 hours,
100 km hr-1,
1263 mm2,
(9 marks)
(b) (i)
Define and state the S.I. unit of measurement for the following quantities
acceleration,
(ii)
Force
State Newton’s First and Second laws.
(iii) A car starts from rest and moves with uniform acceleration over a distance
of 130m in a time of 10 s. Calculate the final velocity and the acceleration
of the car.
(iv)
If the car then stops accelerating and continued to travel at constant
velocity how far will it travel in 8 mins.
(v)
If the driver then spots a car breaking in front and slams on the breaks
which causes the car to decelerate at a rate of –5.4 ms-2. Calculate how
long it will take the car to come to a complete stop and how far the car
will have travelled in this time
(16 marks)
(Total 25 marks)
Question Two
(a)
(i)
Define the term linear momentum and state its S.I. unit of
measurement.
(ii)
State the Principle of Conservation of Linear Momentum.
(iii)
Explain the difference between elastic and inelastic collisions.
(iv)
An object of mass 726 g moving with a steady velocity of 10.55 ms-1
along the + x axis collides with a stationary second object of triple its
mass. If the two masses couple together calculate their common
velocity after the collision.
(v)
(b)
Calculate the total kinetic energy of the masses from part (iv) before
and after the collision. Based on this answer was the collision elastic
or inelastic.
(14 marks)
A ball of mass 1.5 kg is dropped from a window that is 50 m above the
ground.
(i)
How long does it take the ball to fall ?
(ii)
Calculate the kinetic energy of the ball as it hits the ground.
(4 marks)
(c )
Describe in detail an experiment to determine the coefficient of friction
between two surfaces.
(7 marks)
(Total 25 marks)
Question Three
(a)
(i)
Define the terms energy, power and efficiency stating the S.I.
units of measurement of each.
(ii)
State the Law of Conservation of Energy.
(iii)
An engine can raise 240 kg of coal every minute out of a mine
shaft 160m deep. If it is 70% efficient calculate both the work
done by the engine in 1 hour and its power rating.
(11 marks)
(b) Explain how an object moving at constant speed can have a force acting
on it.
(2 marks)
(c) A cd accelerates uniformly from rest to its operational speed of 500 rpm
in 3.7 s. The cd plays for 48 minutes and then comes uniformly to a stop in
4.25 s.
(i)
Convert the operational speed into correct S.I. units.
(ii)
Calculate a value for the angular acceleration of the cd while it is
accelerating.
(iii)
If the diameter of the cd is 120mm calculate its linear velocity at
the edge of the cd at it operational speed.
(iv)
Calculate the linear velocity, at a point in the cd half way between
the edge and the center, again at its operational speed.
(v)
Calculate the number of rotations that the cd makes while it is in
operation.
(vi)
Calculate a value for the angular deceleration while the cd is
coming to a stop.
(vii) Calculate the number of revolutions that the cd makes while it is
coming to a stop.
(12 marks)
Question 4
(a)(i) State Newton’s Third Law of Motion.
(ii) Define the terms Frictional Force and the coefficient of friction and
state its S.I. units.
(5 marks)
(b) (i)Draw a vector diagram to represent all the forces acting on a block of
mass m (
For each force derive the equation for the magnitude of the force and
indicate its direction.
(ii) Derive the equation for the total force acting on the mass down the
incline.
(8 marks)
(c)
(i)
(ii)
How long will it take a mass of 1655 g to slide from rest a distance of
88 cm down a plane inclined at an angle of 45o to the horizontal if
the plane is frictionless
the coefficient of friction is 0.27.
(12 marks)
Section B
Answer at least one Question from this section
Question 5.
(a) (i) Define the terms Density and Pressure stating its SI unit of
measurement of each.
(ii) Derive the expression
P=
(iii) Atmospheric pressure on a particular day is 755mm(Hg). Calculate the
absolute pressure at a depth of 15m in sea-water on that same day.
(11 marks)
(b)(i) State Archimedes Principle.
(ii)
A metal object weighs 6 N in air, 5.2 N in water. Calculate the mass, the
relative density and density of the metal.
(7 marks )
(c)(i) Define Youngs’ Modulus
(ii) A copper wire of length 1.3 m and diameter 0.32 mm is extended when a load of
7.921 kg is applied. Calculate the extension produced and the work done.
(7 marks)
Question 6
(a)
Define the following terms as applied to a wave motion for each quantity
include a diagram:
wavelength,
frequency and periodic time.
(8 marks)
(b)
A source emits a sound of frequency 5000 Hz in air. Calculate its wavelength.
(2 marks)
I
Explain the difference between a transverse and a longitudinal wave, giving
one example of each.
(4 marks)
(d) Define the terms intensity and intensity level of sound stating the S.I.
unit of measurement of each.
(4 marks)
(e) A small source emits sound uniformly in all directions. If the intensity
-2
of the sound is 4
at a point X which is at a distance of 3 m
from the source.
(i) Calculate the intensity level of the source.
(ii) Calculate the intensity level at a point Y a distance of 10 m from the
source.
(7 marks)
PHYSICAL CONSTANTS
g ( acceleration due to gravity)
=
9.81 ms-2
velocity of sound in air
=
340 m s-1
Density of water
=
1000 kg m-3
Density of sea-water
=
1003 kg m-3
Density of mercury
=
13600 kg m-3
=
1 x 10 -12
W m -2
Y(Youngs’ Modulus of copper)
=
110 GN m-2
Some Useful Equations
Linear Motion with constant acceleration
v
s = u t + ½ a t2
= u + a t
Potential Energy.
Kinetic Energy.
=
=
m g h
½ m v2
v2 = u2 + 2 a s
Centripetal acceleration =
v2
r
=
 2r
There are other values and equations on page 40 of the Mathematics (Log)
Tables that you may also find useful.