9K Speeding Up...Newton’s laws of motion
lesson
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Newton and forces
Newton was born December 25th 1642. Between 1664 and 1666, Newton lay the groundwork of
his theory of calculus, laws of motion, theory of colour, and theory of universal gravitation. It is
during these few years that nearly all of Newton's lifetime scientific achievements took shape.
Newton's key insight of 1666, namely that gravity, the force felt here on Earth is the same force
that held the planets in their orbits around the Sun. Newton developed in detail these ideas,
providing a theoretical framework for the Laws of planetary motion. Newton made numerous
discoveries in the field of optics, especially with respect to light and colours. He was knighted in
1705 and died on 20th March 1727.
Sir Isaac Netwon and Newton’s laws:
Newton Newton’s Laws of Motion
Newton’s first Law:
Diagram
Newton’s first law states: ‘An object in motion tends to stay in
motion, and an object at rest tends to stay at rest, unless the
object is acted upon by an outside force.’
Newton’s second Law:
Newton’s second law states that ‘Acceleration = force/mass.’
This law relates the force exerted on an object, its mass and
resulting acceleration.
Notes Newton's ideas were written
Newton’s third Law:
between 1684 and 1686 and
published by Edmond Halley, of Newton’s third law states that: ‘Every action has an equal and
cometary fame. His thesis was
opposite action.’ This law relates how if you’re falling to Earth,
titled: Philosophiae Naturalis
the Earth is also falling toward you !
Principia Mathematica

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Newton’s first law
Newton’s first law states “An object in motion tends to stay in motion, and an object at
rest tends to stay at rest, unless the object is acted upon by an outside force.” For
example, an object at rest will stay at rest unless a force is applied to it. If it is moving,
it will keep on moving at a constant speed and in a straight line. Name two types of
forces acting on a stationary car: Draw a diagram of these forces...are they equal in
size ?
Newton’s first law:
Example one Example two Example three
Diagram
Notes Astronaut at rest: At Rest: Constant speed:
In this example, the astronaut The archer exerts a force by As the probe gains speed, due to
will remain motionless unless using his skeletal muscle on the the pull of gravity, friction due to air
an outside force acts upon him bow and arrow which is equal in resistance increases, so that the
during his space walk. How size but opposite to the elastic two forces are equal, but opposite.
would the astronaut make pull of the bow. What will The probe stops accelerating and
himself go forwards ? happen when he lets go ? travels at a constant speed.

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Newton’s second law one
Newton’s second law states that Acceleration = Force/Mass
Acceleration = Force (N)/ Mass (Kg) Units for acceleration = m/s2
When the forces acting on an object is unbalanced, the resultant force causes the
object to change its speed or velocity. It accelerates or decelerates. How fast it
accelerates or decelerates depends on:
Mass (the more mass an object has, for the same force acting upon it, the less it accelerates)
Resultant Force (the greater the force acting on an object with the same mass, the faster it will accelerate)
Newton’s second law:
Example one Example two Example three
Diagram
1N
1Kg
a = 1m/s2
Notes Having the biggest engine The standard definition of a Buses are slow, although they
and the lightest car gives Newton: One Newton is have a very powerful engine
formula one drivers and their defined as the force which will delivering a lot of force, their
teams an advantage over give an object with the mass of mass is huge when compared
their competitors. 1kg, an acceleration of 1m/s2. to that of a car.

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Newton’s second law two
Working out the acceleration of a moving object with a known fixed mass and a known
force acting on the object is easy. Newton’s second law tell us that the acceleration of
an object is equal to force divided by its mass. Work out the acceleration of the
different moving vehicles which all have different masses and resultant forces acting
upon them...explain why a lorry is slow to accelerate when compared to a bullet or
even a cyclist ?
Acceleration = Force (N)/ Mass (kg) Units for acceleration = m/s2
Working out acceleration:
Lorry Bullet Motorbike Cyclist
Diagram
Force 90,000N 20N 12000N 600N
Mass 30,000kg 0.1kg 800kg 80kg
Acceleration = force/mass Acceleration = force/mass Acceleration = force/mass Acceleration = force/mass
(m/s2)
a= 90,000N/30,000kg _______________________ ? _______________________ ? _______________________ ?
__________m/s2 __________m/s2 __________m/s2
= 3m/s2

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Newton’s third law
Newton’s third law states “Every action has an equal and opposite re-action”
Think about this. If you are falling towards Earth, then Newton’s third law states that there
must be an equal and opposite reaction. Does the Earth move upwards towards you falling
downwards ? Well yes it does, but its mass is huge, so the effect cannot be measured or
seen. Another example, when you shoot a gun, the force that propels the bullet forwards
also pushes you backwards a little. Again there is a great difference between the mass of a
bullet and the person, but the effect can be seen. Why in movies do we know that they
exaggerate this effect ?
Newton’s third law:
Example one Example two Example three
Diagram
Gun shot: Free falling: Rocket:
Notes
The force pushes you As you free fall, the Earth The thrust of the rocket’s engines
backwards, as the bullet experiences an equal and pushes against the Earth. As the
moves forwards from the gun opposite reaction, although rocket moves out to space, Earth
barrel. Movies exaggerate this because of Earth’s huge mass it undergoes an equal and opposite
a great deal for effect ! can’t be observed. reaction.