newton’s 2nd law - · pdf filethis forms the basis of newton’s second law of...
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Newton’s 2nd Law Unbalanced forces cause acceleration
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What links these images….. Write a sentence about each.
..with this
FASTER!
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Balanced or Unbalanced? • Which pairs of arrows go together?
Which pairs are balanced, which are unbalanced? How do you know this?
Decide which way the car is moving. Why do you think this?
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Aim
• To calculate acceleration
• To understand the link between force, mass and acceleration
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The bigger picture
Have you ever wondered
What causes acceleration?
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Balanced and unbalanced forces 1) This animal is either ________ or moving with _____ _____
4) This animal is _______
2) This animal is getting _________
3) This animal is getting ______
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If the resultant force acting on an object is not zero, all the forces are said to be unbalanced.
This forms the basis of Newton’s second law of motion, which states:
What is Newton’s second law?
If the forces on an object are unbalanced, two things about the object can change:
the speed of the object may change – it may either increase or decrease
the direction of motion may change.
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How is movement calculated from force?
The resultant force acting on an object is related to the object’s mass and acceleration. These three factors are linked by the following equation:
Resultant force is measured in newtons (N).
Mass is measured in kilograms (kg).
Acceleration is measured in metres per second per second (m/s2).
force = mass x acceleration
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How do we use Newton’s second law?
A car has a mass of 1,000 kg. What force must the car’s engine supply to cause an acceleration of 2 m/s2?
force = mass x acceleration
= 1,000 x 2
= 2,000 N
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Using a formula triangle A formula triangle helps you to rearrange a formula. The formula triangle for force (f), mass (m) and acceleration (m) is shown below.
x
Cover the quantity that you are trying to work out, which gives the rearranged formula needed for the calculation.
So to find force (f), cover up f…
…which gives the formula…
f = m x a
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How do we use Newton’s second law?
A lorry has a mass of 12,000 kg. What acceleration is caused by a force of 10,000 N?
force = mass x acceleration
= 0.83 m/s2
= 10,000 12,000
force mass
acceleration =
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Force, mass and acceleration 1) A force of 1000N is applied to push
a mass of 500kg. How quickly does it accelerate?
2) A force of 3000N acts on a car to make it accelerate by 1.5m/s2. How heavy is the car?
3) A car accelerates at a rate of 5m/s2. If it weighs 500kg how much driving force is the engine applying?
4) A force of 10N is applied by a boy on a ball of 100g. What is its acceleration?
F
A M
2𝑚/𝑠2
2000kg
2500N
100𝑚/𝑠2
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F = ma calculations
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Resultant force: The resultant force is the single force that can replace a number of forces acting on an object.
Any object can be:
constant velocity
stationary moving
Changing velocity (accelerating/decelerating)
Balanced forces
Balanced forces
Unbalanced forces
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Plenary: Create a mind map or organizer using popplet about resultant forces
Newton’s 2nd Law F = m x a
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