Issy 3rd form Physics Flashcards
Define a scalar quantity and give 2 examples.
It is a quantity which only has size.
temperature, time
Define a vector quantity give 2 examples.
It is a quantity which has size and direction.
force, acceleration.
What is meant by the term velocity
It is a speed in a certain direction
What is the difference between speed and velocity
Speed is a scalar quantity and velocity is a vector quantity.
if we say an aeroplane is travelling at 180m/s then we are describing it’s speed. If we say it’s travelling at 180m/s due east then we are describing its velocity.
What is the difference between distance and displacement?
Distance is a scalar quantity and displacement is a vector.
For example the distance from Thornbury Castle to Warwick castle is 71 miles. If we add a direction of NE then it becomes a displacement.
How is a vector drawn?
vectors are represented by arrows. The size of the arrow represents the magnitude of the vector and the direction is shown by the direction of the arrow.
For example if an object has 2 forces acting on it and one is bigger than the other the arrows will be different lengths. The arrows will show the direction of the force.
What is a force?
A force is a push or a pull. Therefore it is a vector quantity because it has magnitude and direction.
What are the four main contact forces?
- Normal contact force - the force which supports an object resting on a surface eg your phone on a table.
- Friction - two objects sliding past each other. e.g a box sliding down a slope
- Tension- An object that is being stretched experiences a tension force. e.g a rope towing a car
- Air resistance also called drag. It is the force acting on an object moving through the air.e.g a car driving- you can feel it if you hold you hand out of the window.
What is a non contact force?
They are forces which act between objects which are not physically touching each other.
Identify and describe 3 non contact forces.
- Gravitational - Gravity is the force which pull objects down towards the earth.
- Electrostatic. These forces act between any charged particle in an electric field. e.g when you rub a balloon and can stick it to a wall.
- Magnetic - a magnetic force is experienced by any magnetic material in a magnetic field.
What units are used to measure forces?
Newtons (N)
What is gravitational field strength?
The earth produces a gravitational field which pulls objects towards it. Near the surface this is 9.8 N/kg
Describe the term weight, how is it calculated?
Weight describes the pull of gravity on an object
It is calculated as W = mg
Weight = mass x gravitational field strength.
What is the relationship between weight and mass
They are directly proportional, so if your mass decreases so does your weight.
Your weight changes if the gravitational field changes - so in space where there is a very low gravitational field your weight is less but your mass remains the same.
weight ∝ mass
What is the name of the point on an object through which the weight is considered to act.
The centre of mass
