TOPIC 5 - FORCES Flashcards
What is a vector quantity?
Vector quantities have magnitude and a direction.
Give some examples of vector quantities.
force, velocity, displacement, acceleration, momentum etc
What is a scalar quantity?
Only have magnitude but no direction.
Give some examples of scalar quantities.
speed, distance, mass, temperature, time etc
How are vectors usually represented?
By an arrow - the length of the arrow shows the magnitude and the direction shows the direction of the quantity.
What is a force?
A push or pull on an object that is caused by interacting it with something. All forces are either contact or non-contact.
Give examples of contact forces.
friction, air resistance, tension in ropes, normal contact force etc
Give some examples of non-contact forces?
Magnetic force, gravitational force, electrostatic force etc
What is an interaction pair?
A pair of forces that are equal and opposite and act on two interacting objects.
What is gravitational force?
The force of attraction between masses.
It makes all things fall towards the ground, on the surface of a planet
It gives everything weight
What is mass?
Mass is the amount of ‘stuff’ in an object. This will have the same value anywhere in the universe.
What is weight?
The force acting on an object due to gravity (the pull of the gravitational force on the object). Close to Earth, this force is caused by the gravitational field around the Earth. Gravitational field strength varies with location. It is stronger the closer you are to the mass causing the field, and stronger for larger masses. Therefore, the weight of an object changes with location.
What is weight measured in?
Weight is a force measured in Newtons. It is measured using a calibrated spring balance.
What is the relationship between weight and mass?
They are directly proportional.
What is the resultant force?
The resultant force is the overall force on a point or object. If you have a number of forces acting at a single point, you can replace them with a single force (so long as the single force has the same effect as all the original forces together.
If all the forces act along the same line, the overall effect is found by adding those going in the same direction, and subtracting any going in the opposite direction.
When is work done?
When a resultant force moves an object through a distance, energy is transferred and work is done on the object.
The force does work to move the object and energy is transferred from one store to another.
What is the equation for work done?
Work done = force x distance (moved along the line of action of the force) (m)
How is joules converted into newton metres?
1 joule = 1 Nm
One joule of work is done when a force of one newton causes an object to move a distance of one metre.
When is an object in equilibrium?
An object is in equilibrium if the forces on it are balanced. That means that if all the forces acting on an object combine to give a resultant force of zero, the object is in equilibrium.
How can you draw the forces if the force line is at an awkward angle?
Split it into a horizontal and a vertical line.
What are elastic objects?
An object that can be elastically deformed.
What does it mean if an object is inelastically deformed?
An object has been inelastically deformed if it doesn’t return to its original shape and length after the force has been removed.
What is the relationship between extension and force?
Extension and force are directly proportional.
Force = spring constant x extension
When will extension and force no longer be directly proportional?
There is a maximum force above which the graph curves, showing that extension is no longer proportional to force. This is known as the LIMIT OF PROPORTIONALITY