P2.2 - Newton’s laws Flashcards
When do forces arise
Pairs of forces arise when objects interact
What happens in an interaction pair?
each force acts on a different object
The forces are the same size and type
The forces act in opposite directions
What does networks third law state
“ for every action there is an equal and opposite reaction”
This means that forces always come in pairs
What is a non-contact force
A force produced because an object is in a field
The objects don’t need to be touching for the force to act
Charges magnets and masses interact at a distance
What are some non contact forces
Electrostatics
Magnetism
Gravity
What is a field
A field is a region where an electrical charge a magnetic material or a mass experiences a force
How do you represent forces
A force arrow
The length of the arrow shows the magnitude
The direction of the arrow shows the direction of force
An object will deform a surface until the normal contact force balances the weight True or false
True
What is a contact force
A force that only acts when objects are in contact
What are examples of contact forces
Friction
Drag
Normal contact force
Upthrust
Tension
What is an example of friction
Friction on a sliding box
What is an example of drag
Drag on a falling leaf
What is an example of normal contact force
Normal contact force acting on an elephant
What is an example of upthrust
Upthrust on a floating boat
What is an example of tension
Tension in the chord of a bungee jumper
How does friction work
It occurs because the atoms that make up the surfaces interact when rough surfaces slide over each other
What is drag
A force that acts opposite to the direction of the motion of the body
How does drag work (in terms of particles)
The particles of the liquid or gas collide with the object and the object pushes them away
How does normal contact force work
Solid objects deform slightly when you exert a force on them
The bonds between the particles are compressed
How does upthrust work
Gravity produces pressure differences in a fluid
The pressure produces a net upwards force
How does tension work
Solid objects deform slightly when you exert a force on them
The bonds between the particles are stretched
What is a free body diagram
A free body diagram is a diagram that shows the forces acting on a single object
Why do we use free body diagrams
We use them to predict or explain the motion of the object or to do calculations
What is the resultant force
The force when two or more forces are added together as vectors
What is the net force
the force when two or more forces are added together as vectors
What is Newton’s First law?
“An object will continue to stay at rest or move with uniform velocity unless a force acts upon it”
This means it takes a resultant force to change the motion of an object
What will happen to an object is the resultant force is 0
The speed or direction of an object will not change
What is inertia
the measure of how difficult it is to change an object’s velocity
Why do objects move at a steady speed
If the resultant force is 0 then the speed or direction of an object doesn’t change
A steady speed means there is 0 resultant force.
The object will continue to move with a steady velocity if there is no force acting on it
What is equilibrium
An object is in equilibrium if the resultant force is 0
This means that the forces cancel out and the motion does not change
What can a resultant force do?
Change the speed of an object
Change the direction of motion of an object
Change both the speed and direction of motion of an object
What is Newton’s second law of motion
If the resultant force is not 0 the motion of an object changes
The acceleration that the resultant force produces depends on:
- the size of the resultant force
- the mass (inertia) of an object
How do you calculate force
Force (N) = mass (kg) ✖️ acceleration (m/s2)
1N = 1Kgm/s2
True
What happens to the acceleration of an object when it is moving in a circle
An object moving in a circle at a constant speed is accelerating (even though the speed does not change)
It is constantly changing direction so it’s velocity is constantly changing
What is terminal velocity?
The velocity that a moving object reaches when the resultant force is zero
What happens in terms of motion when you skydive
When you jump out of the plane you accelerate and you motion changes because there is a resultant force on you
The air exerts a force (air resistance) on you but the air exerts a larger force (gravity)
As you accelerate the force of the air increases and equals the force of the earth on you so your motion doesn’t change
A parachute increases the force of the air to reduce your velocity.
