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Physics 11 Assignment
Chapter 2
1. Define the following terms:
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scalar
vector
position
displacement
velocity
acceleration
time interval
speed
uniform motion
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non-uniform motion
instantaneous velocity
constant (uniform)
acceleration
non-uniform acceleration
average acceleration
instantaneous acceleration
acceleration due to gravity
2. Can an object have a varying velocity if its speed is constant? Explain.
3. Can an object have a varying speed if its velocity is constant? Explain.
4. When an object moves with constant velocity, does its average velocity during any time
interval differ from its instantaneous velocity at any instant? Explain.
5. Can an object have a northward velocity and a southward acceleration? Explain.
6. As a freely falling object speeds up, what is happening to its acceleration due to gravity?
Does it increase, decrease or stay the same? Explain.
7. If you are driving 110 km/h along a straight road and you look to the side for 2.0 s, how
far do you travel during this inattentive period?
8. You are driving home from school steadily at 65 mph for 130 miles. It then begins to
rain and you slow to 55 mph. You arrive home after driving for 3.0 hours and 20.0
minutes. (a) How far is your hometown from school? (b) What was your average
speed?
9. A bowling ball traveling with constant speed hits the pins at the end of a bowling lane
16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball
is released from his hands. What is the speed of the ball? Note: the speed of sound in
air is 340 m/s.
10. A car accelerates from 12 m/s to 25 m/s in 6.0 s. What is its acceleration? How far did
it travel in this time? Assume constant acceleration.
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Key
1.
scalar - a physical quantity that has only a
magnitude or size
uniform motion - moving at constant velocity
non-uniform motion - the velocity is
changing, either in magnitude or in direction, or
both
vector - a physical quantity that has a
magnitude and a direction
instantaneous velocity - the velocity of an
object at one instant in time; calculated as the
slope of the tangent to the curve of an object’s
position-time graph at that particular time
position – the location of an object with
respect to a reference point
displacement – change in position
velocity - the rate of change of position of an
object in a particular direction
constant (uniform) acceleration acceleration that is not changing over a certain
interval of time
acceleration - the rate of change of velocity of
an object
non-uniform acceleration - the acceleration
that is changing with time
time interval - the amount of time that passes
between two instants of time
average acceleration - another term for
acceleration, calculated as the quotient of the
change in velocity and the time interval over
which the velocity is changing
speed - the distance an object travels divided
by the time the object was travelling; speed is a
scalar quantity
instantaneous acceleration – the
acceleration of an object at a particular time;
calculated as the slope of the tangent to the
curve of an object’s velocity-time graph at that
particular time
acceleration due to gravity - acceleration of
an object towards the centre of a planet due to
the gravitational attraction of the mass of the
planet on the object
2. Can an object have a varying velocity if its speed is constant? Explain.
If an object has constant speed, it can have varying velocity. By definition, velocity is a
vector with magnitude and direction. By maintaining constant speed but changing
direction, velocity can be varied.
3. Can an object have a varying speed if its velocity is constant? Explain.
By definition, if an object has a constant velocity, then both the object's speed and its
direction of motion are constant. Therefore the object CANNOT have a varying speed if its
velocity is constant.
4. When an object moves with constant velocity, does its average velocity during any time interval
differ from its instantaneous velocity at any instant? Explain.
When an object moves with constant velocity, its average velocity over any time interval is
exactly equal to its instantaneous velocity at all times.
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5. Can an object have a northward velocity and a southward acceleration? Explain.
If an object is traveling to the north but slowing down, it has a northward velocity and a
southward acceleration.
6. As a freely falling object speeds up, what is happening to its acceleration due to gravity? Does it
increase, decrease or stay the same? Explain.
As a freely falling object speeds up, its acceleration due to gravity stays the same. If air
resistance is considered, then the acceleration of the object is due to both gravity and air
resistance. The total acceleration gets smaller as the object speeds up, until the object
reaches a terminal velocity, at which time its total acceleration is zero. Thereafter its speed
remains constant.
7. If you are driving 110 km/h along a straight road and you look to the side for 2.0 s, how far do you
travel during this inattentive period?
We find the distance traveled…
(110 km/h)·(2.0 s/3600 s/h) = 0.611 km = 61.1 m
8. You are driving home from school steadily at 65 mph for 130 miles. It then begins to rain and you
slow to 55 mph. You arrive home after driving for 3.0 hours and 20.0 minutes. (a) How far is your
hometown from school? (b) What was your average speed?
We find the elapsed time before the speed change…
Thus the time at the lower speed is…
We find the distance traveled at the lower speed…
55 mi/h)·(1.33 h) = 73 mi.
The total distance traveled is…130 mi + 73 mi = 203 mi.
We find the average speed…
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9. A bowling ball traveling with constant speed hits the pins at the end of a bowling lane 16.5 m long.
The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his
hands. What is the speed of the ball? Note: the speed of sound in air is 340 m/s.
We find the time for the sound to travel the length of the lane…
We find the speed of the bowling ball…
10. A car accelerates from 12 m/s to 25 m/s in 6.0 s. What is its acceleration? How far did it travel in
this time? Assume constant acceleration.
We find the acceleration from
v f  vi  at
25 m/s = 12 m/s + a (6.0 s)
25 m/s - 12 m/s
a
 2.17 m/s2
6.0s
We find the distance traveled from
1
d  (v f  vi )t
2
1
d  (25 m/s + 12 m/s)(6.0s) = 111 m
2
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