beath high school - int 1 physics1 intermediate 1 physics movement forces speed and acceleration...
Post on 20-Jan-2016
235 Views
Preview:
TRANSCRIPT
Beath High School - Int 1 Physics 1
Intermediate 1 Physics
Movement Forces
Speed and acceleration Moving bodies
Beath High School - Int 1 Physics 2
Intermediate 1 Physics
Movement
Forces
Beath High School - Int 1 Physics 3
The unit of force is the n _ _ _ _ _ , symbol N.
Forces can be measured using a n _ _ _ _ _balance.
When a force acts on a spring balance, thespring inside it s _ _ _ _ _ _ _ _ .
The position of the stretched spring on thes _ _ _ _ tells you the size of the force.
n e w t o n
s t r e t c h e s
s c a l e
Measuring force
n e w t o n
Beath High School - Int 1 Physics 4
A newton balance is used to measure
f _ _ _ _ .f o r c e
Weight
_ _ newtons1 0
Beath High School - Int 1 Physics 5
Weight is a f _ _ _ _ .f o r c e
Weight
Weight is the pull of the Earth on an
object due to g _ _ _ _ _ _ .
A 1 kilogram mass (1 kg) has a w _ _ _ _
_
of 10 newtons (10 N).This means the earth p _ _ _ _ the
1 kilogram mass with a force of 10
newtons.
g r a v i t y
w e i g h t
p u l l s
Beath High School - Int 1 Physics 6
For any object we can find its weight
if
we know the mass of the object in
kilograms.
Calculating weight
weight = 10 x
mass(N) (kg
)newtons
kilograms
Beath High School - Int 1 Physics 7
example 1:
Find the weight of a 2 kg bag of
sugar.
Calculating weight
weight = 10 x
mass = 10 x
= N
2
20
The weight of a 2 kg bag of sugar is
N
20
Beath High School - Int 1 Physics 8
example 2:
Find the weight of a 55 kg pupil.
Calculating weight
weight = 10 x
mass = 10 x
= 550 N
55
The weight of a 55 kg pupil is 550 N
Beath High School - Int 1 Physics 9
Friction is a force that opposes the m _ _ _ _ _
of a body.
Friction
m o t i o n
The force of friction can s _ _ _ a movingobject or s _ _ _ it down.
s t o ps l o w
The force of friction can also keep objects from
starting to m _ _ _ .m o v e
Beath High School - Int 1 Physics 10
F _ _ _ _ _ _ _ is caused by the contact of twosurfaces.
Friction
F r i c t i o n
If objects do not slide across each other easily,
the force of friction between the surfaces oftwo objects is l _ _ _ _ .
l a r g e
If the objects slide e _ _ _ _ _ , the force offriction is small.
e a s i l y
Beath High School - Int 1 Physics 11
H _ _ _ FrictionSliding rough surfaces is
like sliding the bristles of twobrushes - it is difficult.
L _ _ FrictionSliding smooth surfaces islike sliding the backs of twobrushes - it is easy.
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 _ _ _ _ _ .
Friction
h i g h
H i g h L o w
s m o o t h
Beath High School - Int 1 Physics 12
The force of friction can be increased by making thesurfaces r _ _ _ _ _ _ or by pressing the surfacesh _ _ _ _ _ together.
Changing Friction
r o u g h e rh a r d e r
The force of friction can be reduced by making thesurfaces s _ _ _ _ _ _ _ or lifting the surfaces awayfrom each other.
s m o o t h e r
Lubrication for example, uses o _ _ which lifts twosurfaces apart and r _ _ _ _ _ _ the force of friction.
o i lr e d u c e s
Air can also be used to lift surfaces aparte.g. in the h _ _ _ _ _ _ _ _ _ .h o v e r c r a f t
Beath High School - Int 1 Physics 13
When an object moves through the air, the air rubsagainst the object causing friction; this air friction iscalled air r _ _ _ _ _ _ _ _ _ .
Streamlining
r e s i s t a n c
eStreamlining 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.
The shape with the least air resistance is theteardrop shape - this is the m _ _ _ streamlined.
a i
rl e s s
m o s t
Beath High School - Int 1 Physics 14
W _ _ _ tunnels are used to improve the streamlining of
cars.
Cars and StreamliningW i n d
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
Beath High School - Int 1 Physics 15
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 balancedforces.
Balanced Forces
Some examples of balanced forces are;
F F
20 N 20 N
opposite
Beath High School - Int 1 Physics 16
Balanced ForcesSome examples of balanced forces are;
F F
30 N 30 N
F
F
15 N
15 N
All of the objects shown above are acted on byb _ _ _ _ _ _ _ forces.b a l a n c e d
Beath High School - Int 1 Physics 17
Examples of balanced forces
When two tug-of-warteams are pulling againsteach other but neither ismaking any progress, thef _ _ _ _ _ applied by eachteam must be balanced.f o r c e s
Beath High School - Int 1 Physics 18
Examples of balanced forces
Before skydivers open theirparachute they fall with a
constantspeed called their t _ _ _ _ _ _ _velocity. This is because theirweight is balanced by thea _ _ r _ _ _ _ _ _ _ _ _ on theirbody.
t e r m i n a l
Air Resistance
Weight
a i r r e s i s t a n c
e
Beath High School - Int 1 Physics 19
Examples of balanced forces
When they open their parachutethey still fall at a constant speedbut much slower than beforebecause the air resistance isg _ _ _ _ _ _ with the parachuteopen.
Air Resistance
WeightThe air resistance is still e _ _ _ _to the weight so the forces are
stillbalanced.
e q u a l
g r e a t e r
Beath High School - Int 1 Physics 20
Examples of balanced forces
When a plane is travellingforwards, the air rushing overthe wings creates anu _ _ _ _ _ force.u p w a r d
Upward Force
Weight
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, theupward and downward forces are n _ _
balanced.n o t
Beath High School - Int 1 Physics 21
Intermediate 1 Physics
MovementSpeed and acceleration
Beath High School - Int 1 Physics 22
We can measure the average speed of any object bymeasuring the d _ _ _ _ _ _ _ it travels and the t _ _ _it takes to travel that distance.
Measuring average speed
d i s t a n c e t i m e
Average speeds are usually measured over l _ _ _ _distances or l _ _ _ times.
l a r g e
l o n g
Beath High School - Int 1 Physics 23
The average speed can then be found using the following
equation:
Measuring average speed
Average speed =distance
time
metres (m)
seconds (s)metres per second
(m/s)
Beath High School - Int 1 Physics 24
The distance can be measured using a tape or m _ _ _ _
stick.
Measuring average speed
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
Beath High School - Int 1 Physics 25
Automatic timers are oftenoperated by light g _ _ _ _ .
Measuring average speed
g a t e s
1 2 4 6
lightgate 1
lightgate 2
Timer
When a moving object cutsthe beam of light gate 1,
thetimer 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, the average speed
=
distance between gatestime on timer
Beath High School - Int 1 Physics 26
1. A car travels a distance of 45 m in 30 s.Calculate its average speed.
Examples on calculating speed
45
Average speed =distance
time
=30
= 1.5 m/s
Beath High School - Int 1 Physics 27
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?
Examples on calculating speed
2.5
Average speed =distance
time
=15
= 0.167 m/s
Beath High School - Int 1 Physics 28
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?
Examples on calculating speed
1.2
Average speed =distance
time
=0.8
= 1.5 m/s
Beath High School - Int 1 Physics 29
Your speed at any particular point during a journey iscalled the instantaneous speed - the speed at an
instant.
Instantaneous Speed
Calculating this speed is the same as calculating theaverage speed but the time interval must be very s _ _
_ _.s m a l
l
Beath High School - Int 1 Physics 30
Measuring Instantaneous Speed
Because the time to be measured is so small, there is a
problem with r _ _ _ _ _ _ _ time (the time taken by aperson to start and stop a timer).
r e a c t i o n
0 . 4 6
Millisecond TimerLight gate
To Supply
Trolley
Card
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
eThe trolley is fitted with a card. The timer measures the
t _ _ _ the card cuts off the beam of light.t i m e
Beath High School - Int 1 Physics 31
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
0 . 4 6
Millisecond TimerLight gate
To Supply
Trolley
Card
Beath High School - Int 1 Physics 32
Measuring Instantaneous Speed
0 . 4 6
Millisecond TimerLight gate
To Supply
Trolley
Card
The instantaneous speed is calculated using the length of
card as the d _ _ _ _ _ _ _ and the timer reading as thetime, i.e.
d i s t a n c e
Instantaneous speed =length of card
time on timer
metres (m)
seconds (s)metres per second (m/s)
Beath High School - Int 1 Physics 33
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 thetrolley when it passes the light gate.
= 4.0 m/s
Instantaneous speed =length of card
time on timer=
0.100.025
Beath High School - Int 1 Physics 34
Acceleration is the change of speed of an object inone s _ _ _ _ _ .
Acceleration
s e c o n d
If an object is getting f _ _ _ _ _ , it is accelerating –the speed of the object is increasing.
f a s t e r
If an object is getting s _ _ _ _ _ , it is decelerating –the speed of the object is decreasing.
s l o w e r
Do not confuse acceleration with speed.
A car can be travelling at a h _ _ _ speed but have zero
acceleration;
h i g h also a car can have a high
acceleration butbe travelling at a low s _ _ _ _
s p e e d(though its speed will not stay low for
long!).
Beath High School - Int 1 Physics 35
Car manufacturers often state a value for their car'sacceleration to indicate its performance.
Car performance
The usual performance figure quoted is the t _ _ _ inseconds it takes for the car to increase its speed
fromrest to 60 mph.
t i m e
The smaller the time, the h _ _ _ _ _ the accelerationand the higher the performance.
h i g h e r
A high performance car might be
quoted as: 0-60 mph in 5.0 s
Beath High School - Int 1 Physics 36
The table below shows performance figures for some makes of car.
Car performance
Questions:a. Which car has the greatest acceleration?
Explain your answer. b. Which car has the smallest acceleration?
Explain your answer.
Make of Car I ncrease in Speed
Time for increase
Mini 0—> 60 mph 10.5 seconds
Volvo 0—> 60 mph 19.6 seconds
Ford 0—> 60 mph 8.1 seconds
J aguar 0—> 60 mph 6.1 seconds
Beath High School - Int 1 Physics 37
The table below shows performance figures for some makes of car.
Car performance
Make of Car I ncrease in Speed
Time for increase
Mini 0—> 60 mph 10.5 seconds
Volvo 0—> 60 mph 19.6 seconds
Ford 0—> 60 mph 8.1 seconds
J aguar 0—> 60 mph 6.1 seconds
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.
Beath High School - Int 1 Physics 38
The table below shows performance figures for some makes of car.
Car performance
Make of Car I ncrease in Speed
Time for increase
Mini 0—> 60 mph 10.5 seconds
Volvo 0—> 60 mph 19.6 seconds
Ford 0—> 60 mph 8.1 seconds
J aguar 0—> 60 mph 6.1 seconds
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.
Answers:
Beath High School - Int 1 Physics 39
Intermediate 1 Physics
Movement
Moving Bodies
Beath High School - Int 1 Physics 40
When an object has its speed c _ _ _ _ _ _ by anotherobject, we say the two objects collide.
Collisionsc h a n g e d
MOVING BODIES
Suppose object A is moving and collides with object B.
A B
The effect of the collision is to change the speeds ofb _ _ _ the colliding objects.b o t hThe change in speed of the colliding objects is
greaterwhen:a) the objects are moving f _ _ _ _ _ before collisionb) the objects have a larger m _ _ _ .
f a s t e r
m a s s
Beath High School - Int 1 Physics 41
When an object has its speed changed, we say it hasbeen acted on by a f _ _ _ _ .
Change in speed
f o r c e
(Forces occur during collisions).
The larger the force the g _ _ _ _ _ _ the change in the
speed.
g r e a t e r
The longer the time a force is applied the greater is the
c _ _ _ _ _ of speed.c h a n g e
Beath High School - Int 1 Physics 42
When an object is thrown or fired, it travels a distance
horizontally before hitting the ground.
The range of a ball
Eventually even the fastest thrown or fired object hits
the ground due to the force of g _ _ _ _ _ _ pulling itdown.
g r a v i t y
This horizontal distance travelled is called the r _ _ _ _ ,
r a n g
ei.e.
range
Beath High School - Int 1 Physics 43
The range of a ball thrown or hit is changed by:
The range of a ball
a) the s _ _ _ _ the ball is thrown or hits p e e d(the f _ _ _ _ _ the speed the greater the
range)f a s t e r
b) the a _ _ _ _ at which the ball is thrown or hit.a n g l e
Beath High School - Int 1 Physics 44
The range of a ball
The distance (r _ _ _ _ ) a golfball travels depends on thespeed of the club and the loft(a _ _ _ _ ) of the club.
The driver is designed to givethe greatest speed at the
bestangle for maximumd _ _ _ _ _ _ _ .
r a n g e
a n g l e
d i s t a n c e
Beath High School - Int 1 Physics 45
Whenever a ball bounces, it l _ _ _ _ some of its energy
so it never reaches the same h _ _ _ _ _ again.
Height of reboundl o s e sh 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:a) its speed on impact is l _ _ _ _
b) the surface it hits is h _ _ _ .
l a r g e
h a r d
Beath High School - Int 1 Physics 46
Intermediate 1 Physics
Movement
End of Unit
top related