Intermediate 1 Physics

1
Intermediate 1 Physics

• Movement

• Forces

• Speed and acceleration

• Moving bodies

2
Intermediate 1 Physics

• Movement

• Forces

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Measuring force
Forces can be measured using a n _ _ _ _
_ balance.
n e w t o n
When a force acts on a spring balance, the spring
inside it s _ _ _ _ _ _ _ _ .
s t r e t c h e s
The position of the stretched spring on the s _ _
_ _ tells you the size of the force.
s c a l e
The unit of force is the n _ _ _ _ _ , symbol N.
n e w t o n
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Weight

• A newton balance is used to measure
• f _ _ _ _ .

f o r c e
_ _ newtons
1 0
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Weight

• Weight is a f _ _ _ _ .

f o r c e
Weight is the pull of the Earth on an object due
to g _ _ _ _ _ _ .
g r a v i t y
A 1 kilogram mass (1 kg) has a w _ _ _ _ _ of 10
newtons (10 N).
w e i g h t
This means the earth p _ _ _ _ the 1 kilogram
mass with a force of 10 newtons.
p u l l s
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Calculating weight

• For any object we can find its weight if
• we know the mass of the object in
• kilograms.

weight 10 x mass
(kg)
(N)
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Calculating weight

• example 1
• Find the weight of a 2 kg bag of sugar.

weight 10 x mass
10 x
2
N
20
The weight of a 2 kg bag of sugar is N
20
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Calculating weight

• example 2
• Find the weight of a 55 kg pupil.

weight 10 x mass
10 x
55
550 N
The weight of a 55 kg pupil is 550 N
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Friction
m o t i o n

• Friction is a force that opposes the m _ _ _ _ _
  
• of a body.

s t o p
The force of friction can s _ _ _ a
moving object or s _ _ _ it down.
s l o w
The force of friction can also keep objects
from starting to m _ _ _ .
m o v e
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Friction
F r i c t i o n

• F _ _ _ _ _ _ _ is caused by the contact of two
• surfaces.

If objects do not slide across each other
easily, the force of friction between the
surfaces of two objects is l _ _ _ _ .
l a r g e
e a s i l y
If the objects slide e _ _ _ _ _ , the force
of friction is small.
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Friction

• When the force of friction between surfaces is
• h _ _ _ , we say they are rough, when the force
• of friction is low, we say they are s _ _ _ _ _ .

h i g h
s m o o t h
H i g h
L o w
H _ _ _ Friction Sliding rough surfaces is
like sliding the bristles of two brushes - it is
difficult.
L _ _ Friction Sliding smooth surfaces
is like sliding the backs of two brushes - it is
easy.
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Changing Friction

• The force of friction can be increased by making
  the
• surfaces r _ _ _ _ _ _ or by pressing the
  surfaces
• h _ _ _ _ _ together.

r o u g h e r
h a r d e r
The force of friction can be reduced by making
the surfaces s _ _ _ _ _ _ _ or lifting the
surfaces away from each other.
s m o o t h e r
o i l
Lubrication for example, uses o _ _ which lifts
two surfaces apart and r _ _ _ _ _ _ the force of
friction.
r e d u c e s
Air can also be used to lift surfaces apart e.g.
in the h _ _ _ _ _ _ _ _ _ .
h o v e r c r a f t
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Streamlining

• When an object moves through the air, the air
  rubs
• against the object causing friction this air
  friction is
• called air r _ _ _ _ _ _ _ _ _ .

r e s i s t a n c e
Streamlining is when you change the shape of the
object to r _ _ _ _ _ the air resistance.
r e d u c e
The lines in wind tunnel tests show the pattern
of a _ _ flow. The smoother the air flow, the l _
_ _ the air resistance.
a i r
l e s s
The shape with the least air resistance is
the teardrop shape - this is the m _ _ _
streamlined.
m o s t
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Cars and Streamlining
W i n d

• W _ _ _ tunnels are used to improve the
  streamlining of
• cars.

The shape of a car can be made like a teardrop or
like an aeroplane wing to r _ _ _ _ _ air
resistance.
r e d u c e
Sometimes a spoiler is fitted at the back to
improve the air f _ _ _ making it more
streamlined.
f l o w
Another way to reduce air resistance is to make
the car closer to the g _ _ _ _ _ .
g r o u n d
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Balanced Forces

• When two forces are the same size as each other
  and
• act on the same object but in
  directions, they
• balance each other. The forces are called
  balanced
• forces.

opposite
Some examples of balanced forces are
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Balanced Forces
Some examples of balanced forces are
All of the objects shown above are acted on by b
_ _ _ _ _ _ _ forces.
b a l a n c e d
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Examples of balanced forces
When two tug-of-war teams are pulling
against each other but neither is making any
progress, the f _ _ _ _ _ applied by each team
must be balanced.
f o r c e s
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Examples of balanced forces
Before skydivers open their parachute they fall
with a constant speed called their t _ _ _ _ _ _
_ velocity. This is because their weight is
balanced by the a _ _ r _ _ _ _ _ _ _ _ _ on
their body.
t e r m i n a l
a i r
r e s i s t a n c e
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Examples of balanced forces
When they open their parachute they still fall at
a constant speed but much slower than
before because the air resistance is g _ _ _ _ _
_ with the parachute open.
g r e a t e r
e q u a l
The air resistance is still e _ _ _ _ to the
weight so the forces are still balanced.
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Examples of balanced forces
When a plane is travelling forwards, the air
rushing over the wings creates an u _ _ _ _ _
force.
u p w a r d
When the plane is flying level, this upward force
balances the w _ _ _ _ _ of the plane.
w e i g h t
When the plane is taking off and landing,
the upward and downward forces are n _ _ balanced.
n o t
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Intermediate 1 Physics

• Movement

• Speed and acceleration

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Measuring average speed

• We can measure the average speed of any object by
• measuring the d _ _ _ _ _ _ _ it travels and the
  t _ _ _
• it takes to travel that distance.

t i m e
d i s t a n c e
l a r g e
Average speeds are usually measured over l _ _ _
_ distances or l _ _ _ times.
l o n g
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Measuring average speed

• The average speed can then be found using the
  following
• equation

distance
Average speed
time
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Measuring average speed

• The distance can be measured using a tape or m _
  _ _ _
• stick.

m e t r e
Time is measured by a s _ _ _ _ _ _ _ _ or
sometimes by a timer which starts and stops
automatically.
s t o p w a t c h
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Measuring average speed

• Automatic timers are often
• operated by light g _ _ _ _ .

g a t e s
When a moving object cuts the beam of light gate
1, the timer s _ _ _ _ _ timing.
s t a r t s
When the moving object cuts the beam of light
gate 2, the timer s _ _ _ _ timing.
s t o p s
In this case,
distance between gates
the average speed
time on timer
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Examples on calculating speed

• 1. A car travels a distance of 45 m in 30 s.
• Calculate its average speed.

45
30
1.5 m/s
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Examples on calculating speed

• 2. A trolley passes through two light gates which
  are 2.5 metres apart.
• The timer measures a time of 15 seconds.
• What is the average speed of the trolley?

2.5
15
0.167 m/s
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Examples on calculating speed

• 3. A trolley passes through two light gates which
  are 1.2 metres apart.
• The timer measures a time of 0.8 seconds.
• What is the average speed of the trolley?

1.2
0.8
1.5 m/s
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Instantaneous Speed

• Your speed at any particular point during a
  journey is
• called the instantaneous speed - the speed at an
  instant.

Calculating this speed is the same as calculating
the average speed but the time interval must be
very s _ _ _ _.
s m a l l
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Measuring Instantaneous Speed
Because the time to be measured is so small,
there is a problem with r _ _ _ _ _ _ _ time (the
time taken by a person to start and stop a timer).
r e a c t i o n
To measure the speed of a moving trolley, it is
better to use a l _ _ _ _ g _ _ _ because there
is no reaction time.
l i g h t g a t e
The trolley is fitted with a card. The timer
measures the t _ _ _ the card cuts off the beam
of light.
t i m e
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Measuring Instantaneous Speed
It s _ _ _ _ _ when the card cuts the light gate
beam and it stops again when the beam is remade.
s t a r t s
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Measuring Instantaneous Speed
The instantaneous speed is calculated using the
length of card as the d _ _ _ _ _ _ _ and the
timer reading as the time, i.e.
d i s t a n c e
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Example on instantaneous speed
A trolley is fitted with a card 0.10 m in length.
The trolley is set in motion and the card cuts a
light gate. The time on the timer is 0.025
seconds. Calculate the speed of the trolley when
it passes the light gate.
4.0 m/s
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Acceleration

• Acceleration is the change of speed of an object
  in
• one s _ _ _ _ _ .

s e c o n d
f a s t e r
If an object is getting f _ _ _ _ _ , it is
accelerating the speed of the object is
increasing.
s l o w e r
If an object is getting s _ _ _ _ _ , it is
decelerating the speed of the object is
decreasing.
Do not confuse acceleration with speed.
h i g h
A car can be travelling at a h _ _ _ speed but
have zero acceleration
also a car can have a high acceleration
but be travelling at a low s _ _ _ _
s p e e d
(though its speed will not stay low for long!).
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Car performance

• Car manufacturers often state a value for their
  car's
• acceleration to indicate its performance.

t i m e
The usual performance figure quoted is the t _ _
_ in seconds it takes for the car to increase its
speed from rest to 60 mph.
h i g h e r
The smaller the time, the h _ _ _ _ _ the
acceleration and the higher the performance.
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Car performance

• The table below shows performance figures for
  some makes of car.

Questions a. Which car has the greatest
acceleration? Explain your answer. b. Which car
has the smallest acceleration? Explain your
answer.
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Car performance

• The table below shows performance figures for
  some makes of car.

Answers
a. The car with the greatest acceleration is the
Jaguar because it has the shortest time to make
the same increase in speed as all the others.
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Car performance

• The table below shows performance figures for
  some makes of car.

Answers
b. The car with the smallest acceleration is the
Mini because it has the longest time to make the
same increase in speed as all the others.
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Intermediate 1 Physics

• Movement

• Moving Bodies

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Collisions
MOVING BODIES
c h a n g e d

• When an object has its speed c _ _ _ _ _ _ by
  another
• object, we say the two objects collide.

Suppose object A is moving and collides with
object B.
The effect of the collision is to change the
speeds of b _ _ _ the colliding objects.
b o t h
The change in speed of the colliding objects is
greater when
f a s t e r
a) the objects are moving f _ _ _ _ _ before
collision
m a s s
b) the objects have a larger m _ _ _ .
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Change in speed

• When an object has its speed changed, we say it
  has
• been acted on by a f _ _ _ _ .

f o r c e
(Forces occur during collisions).
g r e a t e r
The larger the force the g _ _ _ _ _ _ the change
in the speed.
The longer the time a force is applied the
greater is the c _ _ _ _ _ of speed.
c h a n g e
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The range of a ball

• When an object is thrown or fired, it travels a
  distance
• horizontally before hitting the ground.

Eventually even the fastest thrown or fired
object hits the ground due to the force of g _ _
_ _ _ _ pulling it down.
g r a v i t y
r a n g e
This horizontal distance travelled is called the
r _ _ _ _ ,
i.e.
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The range of a ball

• The range of a ball thrown or hit is changed by

s p e e d
a) the s _ _ _ _ the ball is thrown or hit
f a s t e r
(the f _ _ _ _ _ the speed the greater the range)
a n g l e
b) the a _ _ _ _ at which the ball is thrown or
hit.
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The range of a ball
r a n g e
The distance (r _ _ _ _ ) a golf ball travels
depends on the speed of the club and the loft (a
_ _ _ _ ) of the club.
a n g l e
The driver is designed to give the greatest speed
at the best angle for maximum d _ _ _ _ _ _ _ .
d i s t a n c e
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Height of rebound
l o s e s

• Whenever a ball bounces, it l _ _ _ _ some of its
  energy
• so it never reaches the same h _ _ _ _ _ again.

h e i g h t
A ball dropped from a height of 80 cm might
rebound to height of 50 cm.
It will never rebound to a height of 80 cm.
When a ball hits a surface, it will rebound to a
greater height if
l a r g e
a) its speed on impact is l _ _ _ _
h a r d
b) the surface it hits is h _ _ _ .
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Intermediate 1 Physics

• Movement

End of Unit