FORCES IN ACTION

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FORCES IN ACTION
UNIT 2
MACHINES MOVE THE WORLD
Marta Vidal Vidal
L3 L4 L5 L6
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ISAAC NEWTON (1642-1727)

• FIRST LAW OF MOTION. INERTIA
• An object at rest stays at rest,
• an object in motion stays in motion.

Why does an object stop its motion?
Why do objects change its direction?
Because it is the result of an UNBALANCED FORCE
applied upon an object.
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Unbalanced force

• Start motion
• Stop motion
• Change direction
• Change shape

4
Balanced force

• No change
• No visible effect

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WHICH FORCES INFLUENCE MOTION?

• Contact forces
• Friction
• Push/Pull
• Weight
• Non-contact forces
• Gravity
• Magnetism superconducting

FORCE is any influence that causes a free body
to undergo a change in speed, a change in
direction, or a change in shape.
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HANDS ON! Friction

• PROBLEM
• How do different surfaces affect the movement of
  the objects?
•  
• MATERIALS
• Pencil, toy car, metric tape, 4 clothespegs,
  tape, scissors, aluminium foil, wax paper,
  recycled paper, sand paper, a calculator and
  plastic cable covers.
•  
• STEPS
• 1. Predict the distance of the toy car on each
  surface.
• 2. Create a ramp using 4 clothespegs and plastic
  cable covers.
• 3. Drop the toy car and measure the distance.
• 4. Do 3 different trials for each surface and
  calculate total distance.
•  
•  
•  
• Play with friction

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HANDS ON! Friction

• PROBLEM
• How do different surfaces affect the movement of
  the objects?
• STEPS
• 1. Predict the distance of the toy car on each
  surface.

SURFACE PREDICTION cm TRIAL 1 cm TRIAL 2 cm TRIAL 3 cm DISTANCE T1T2T3 3
Aluminium foil         cm
Wax paper         cm
Recycled paper         cm
Sand paper         cm
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HANDS ON! Friction

• PROBLEM
• How do different surfaces affect the movement of
  the objects?
•  
• STEPS
• 2. Create a ramp using 4 clothespegs and plastic
  cable covers.
•  
•  
•  

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HANDS ON! Friction

• PROBLEM
• How do different surfaces affect the movement of
  the objects?
•  
• STEPS
• 3. Drop the toy car and measure the distance.
• 4. Do 3 different trials for each surface and
  calculate the total distance.
•  
•   

Total distance trial 1 trial 2 trial 3
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SURFACE PREDICTION cm TRIAL 1 cm TRIAL 2 cm TRIAL 3 cm DISTANCE T1T2T3 3
Aluminium foil         cm
Wax paper         cm
Recycled paper         cm
Sand paper         cm
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WEIGHT
ENGLISH DECIMALS IS IN . (DOT) SPANISH DECIMALS
IS IN , (COMMA)

• MASS is a measurement of how much matter is in an
  object.
• WEIGHT is a measurement of how hard gravity is
  pulling on that object.
• On Earth 1 kg of mass 9.8 newtons
• Gravity on Earth is 1G 9.8 newtons
• WEIGHT MASS x GRAVITY
• WEIGHT 1kg x 1 1
• WEIGHT 1 Kg or
  is 9.8 newtons
• On Earth our mass is equal to our weight.
• MASS 1kg WEIGHT 1kg

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• Our MASS is the same everywhere but if we travel
  over the universe we have a different WEIGHT

What will happen to our weight if we travel
around space?
MASS 60 Kg WEIGHT 60 Kg
MASS 60 Kg WEIGHT 60 x 0.16 WEIGHT 9.6 Kg
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Calculate your weight in the Solar System
Look at the gravity of the planets, the sun and
the Moon and calculate your weight in respect to
those.
Planets, Star and satellite GRAVITY MULTIPLIED BY your MASS IS EQUAL TO your WEIGHT
Sun 27,90 MULTIPLIED BY   IS EQUAL TO  
Mercury 0,37 MULTIPLIED BY   IS EQUAL TO  
Venus 0,88 MULTIPLIED BY   IS EQUAL TO  
Earth 1,00 MULTIPLIED BY   IS EQUAL TO  
Mars 0,38 MULTIPLIED BY   IS EQUAL TO  
Jupiter 2,64 MULTIPLIED BY   IS EQUAL TO  
Saturn 1,15 MULTIPLIED BY   IS EQUAL TO  
Uranus 0,16 MULTIPLIED BY   IS EQUAL TO  
Neptune 1,22 MULTIPLIED BY   IS EQUAL TO  
Moon 0,16 MULTIPLIED BY   IS EQUAL TO  
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Look at your results and underline the correct
part of the sentence.
Is it your weight different or is it equal? Is it your weight different or is it equal? Is it your weight different or is it equal? Is it your weight different or is it equal? Is it your weight different or is it equal?
My weight My weight never changes. changes. never changes. changes.  
  Is it your mass different or is it equal?   Is it your mass different or is it equal?   Is it your mass different or is it equal?   Is it your mass different or is it equal?   Is it your mass different or is it equal?
My mass never changes. changes. never changes. changes.    
Calculate your weight in newtons
On Earth On the moon
Weight mass x gravity in newtons Weight mass x gravity in newtons
WEIGHT . x 9,8 WEIGHT . x 1,5
WEIGHT .....newtons WEIGHT .....newtons
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WHAT IS FORCE?

• It can be a PUSH or a PULL.

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Is it a push or a pull?
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ISAAC NEWTON (1642-1727)

• SECOND LAW OF MOTION.

THE UNIT FOR THE FORCE IS IN NEWTONS
The strength of a force is equal to the amount of
the mass involved multiplied by any acceleration
applied to it. F m x a If the mass is bigger
the effect of the FORCE is smaller If the
mass is smaller the effect of the FORCE is
bigger
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HANDS ON! Newtons
MATERIALS - Pencil - Tape measure - Weighing
scale - Dynamometer - 3 objects.
PROBLEM How do you use a dynamometer? What is
the relationship between mass and force?
STEPS 1. Predict the power of the force needed
to move the objects. Write a number from 1 to 3
(from bigger force to a smaller force).
Objects PREDICTION MASS FORCE NEWTONS Result
         
         
         
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HANDS ON! Newtons
MATERIALS - Pencil - Tape measure - Weighing
scale - Dynamometer - 3 objects.
PROBLEM How do you use a dynamometer? What is
the relationship between mass and force?
STEPS 2. Measure the objects with a weighing
scale and record it in your data table.
Objects PREDICTION MASS FORCE NEWTONS Result
         
         
         
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HANDS ON! Newtons
MATERIALS - Pencil - Tape measure - Weighing
scale - Dynamometer - 3 objects.
PROBLEM How do you use a dynamometer/spring
scale? What is the relationship between mass and
force?
STEPS 3. Put a tape measure on the floor and
measure 100 cm in straight line. 4. Attach the
object to the dynamometer and pull it along a
distance of 100 cm and record the result in your
data table.
Objects PREDICTION MASS FORCE NEWTONS Result
         
         
         
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HANDS ON! Newtons
MATERIALS - Pencil - Tape measure - Weighing
scale - Dynamometer - 3 objects.
PROBLEM How do you use a dynamometer? What is
the relationship between mass and force?
STEPS 5. Write your conclusion about the
experiment. 6. Share and check the results with
the whole class.
Write your CONCLUSIONS Write your CONCLUSIONS Write your CONCLUSIONS Write your CONCLUSIONS
If the mass of an object is bigger smaller the force needed to move it is bigger smaller.
If the mass of an object is bigger the force
needed to move it is bigger.
If the mass of an object is smaller the force
needed to move it is smaller.
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ISAAC NEWTON (1642-1727)
THIRD LAW OF MOTION ACTION AND
REACTION All forces occur in pairs. For
every action that takes place there is an equal
and opposite reaction.
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FORCE
It is any influence that causes a free body to
undergo a change in speed, a change in direction,
or a change in shape.
CONTACT FORCES
It is a force that acts at the point of contact
between two objects.
It is the force resisting the relative motion of
solid surfaces, fluid layers, and/or material
elements sliding against each other.
FRICTION
PULL
It is a force that can move something towards
somebody/something.
PUSH
It is a force that can move something away from
somebody/something.
NON-CONTACT FORCES
It is a force applied to an object by another
body that is not in direct contact with it.
MAGNETISM
Force of attraction or repulsion acting between
ferromagnetic materials like iron.
It is a force that pulls all objects towards the
center of the Earth.
GRAVITY