Topic 5 - Forces Flashcards
What quantity is a force?
Vector.
What are vectors?
Quantities with magnitude and direction.
What are examples of vectors?
Force, velocity, displacement, acceleration, momentum…
What are scalars?
Quantities with magnitude but no direction.
What are examples of scalar quantities?
Speed, distance, mass, temperature, time…
How are vectors usually represented?
By an arrow - the length 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 it interacting with something. They are either contact or non-contact.
What is a contact force?
When two objects have to be touching for a force to act.
What are examples of contact forces?
Friction, air resistance, tension, normal contact force..
What is a non-contact force?
The objects do not need to be touching for the force to act.
What are examples of non-contact forces?
Magnetic force, gravitational force, electrostatic force…
What is an interaction pair?
A pair of forces that are equal and opposite and act on two interacting objects.
What are the two important effects of gravity?
On the surface of a planet, it makes all things fall towards the ground. It gives everything weight.
What is mass?
The amount of ‘stuff’ in an object. Will have the same value anywhere.
What is weight?
The force acting on an object due to gravity (the pull of the gravitational force on the object). Measured in newtons.
Describe gravitational field strength.
It varies with location. It is stronger the closer you are to the mass causing the field and stronger for larger masses.
Where is the centre of mass for a uniform object?
At the centre of the object.
How is weight measured?
Using a calibrated spring balance or newton meter.
How is mass measured?
In kilograms with a mass balance.
How can you calculate the weight of an object?
Weight (N) = Mass (kg) x gravitational field strength (N/kg).
What is the gravitational field strength on earth and moon?
Earth = 9.8 N/kg, Moon = 1.6 N/kg.
What happens when you increase the mass of an object?
Increases the weight. Weight and mass are directly proportional.
What is a free body diagram?
A diagram which shows all the forces acting on an object.
What is a resultant force?
When two or more forces act on an object, the resultant force can be found by adding up the individual forces.