beath high school - int 1 physics1 intermediate 1 physics movement forces speed and acceleration...

Beath High School - Int 1 Physics 1

Intermediate 1 Physics

Movement Forces

Speed and acceleration Moving bodies



Movement

Forces


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


A newton balance is used to measure

f _ _ _ _ .f o r c e

Weight

_ _ newtons1 0


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


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


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


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


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


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


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


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


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


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


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


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


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



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



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



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



MovementSpeed and acceleration


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


The average speed can then be found using the following

equation:


Average speed =distance

time

metres (m)

seconds (s)metres per second

(m/s)


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


Automatic timers are oftenoperated by light g _ _ _ _ .


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


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

Examples on calculating speed

45


time

=30

= 1.5 m/s


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


time

=15

= 0.167 m/s


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


time

=0.8

= 1.5 m/s


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


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



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


To Supply

Trolley

Card



0 . 4 6


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)


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


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!).


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


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



Car performance


Time for increase





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.



Car performance


Time for increase





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:



Movement

Moving Bodies


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


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


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


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


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


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



Movement

End of Unit

beath high school - int 1 physics1 intermediate 1 physics movement forces speed and acceleration...

Documents

o o t hbeath high school

o o t h e rlubrication

o t i o nthe force of

r e s i s t

h o v e r c r

o wthe force of friction

s t o ps

o v ebeath high school