P5 - Forces Flashcards
What is a vector? Give some examples
A measurement with quantity AND direction.
FORCES, velocity, displacement, acceleration, momentum are vector quantities
For an arrow showing the vector quantity of something, what do the length and direction show?
The length shows the magnitude (larger arrow, more force)
The direction shows the direction of the quantity
Which direction is -v?
Backwards/ to the left/
Give the definition of a force
A push or a pull on an object caused by it interacting with something. All forces are either contact or non-contact
What type of force is it when 2 objects have to be touching for a force to act?
Contact force
What type of force is when the objects do not need to be touching for the force to act?
Non-contact force
Name some contact and non-contact forces
Contact - friction, air resistance, tension in ropes, normal contact force
Non-contact - magnetic force, gravitational, electrostatic
An equal but opposite force of attraction is felt by both the sun and the Earth/ What is this force?
Gravitational force - non-contact
An equal but opposite forces are felt by both a chair and the ground. But what is this force?
Normal contact force- a chair exerts a force on the ground, whilst the ground pushes back at the chair with the same force
What is gravitational force?
What are the 2 important effects?
The force of attraction between masses
On the surface of a planet, it makes all things fall toward the ground, and it gives everything a weight
What are the differences between weight and mass?
Mass has the same value anywhere in the universe (kg)
Weight is the force acting upon an object due to gravity - the pull of the gravitational force on the object. (N)
Name some factors that make the gravitational field strength stronger
It’s stronger the closer you are to the mass causing he field (earth’s core here). And, stronger for larger masses
The weight of an object will never change True or false?
False - it changes with its location, as it depends on the strength of the gravitational field at the location of the object
Give the formula for weight, and how it is measured
Weight = Mass x Gravitational field strength
N = kg x N/kg
Measured using a calibrated spring, whereas mass is measured with a mass balance
What is a uniform object?
One that has he same density throughout its regular shape - its centre of mass is at the centre
Weight and mass are:
a) directly proportional
b) indirectly proportional
a) directly proportional
Talk about the forces acting upon a skydiver
Weight pulls them towards the ground
Drag (air resistance) acts in the opposite direction to their motion. It is weaker, so the skydiver will be slower with a drag but still fall
What is a free body diagram?
Where it has a picture of an object, and force arrows coming off it - the sizes of the arrows show relative magnitudes of the forces, and the directions show the directions of the forces acting on the object
What is resultant force?
The overall force on a point or an object.
If you have a number of forces acting at a single point, you can replace them with a single, Resultant force (as long as that has the same effect as all the original forces together)
1500 ^ N | 1200N 1000N | 1500 N Calculate the resultant force from the free body diagram
Vertical = 1500 - 1500 = 0N (no resultant force) Horizontal = 1200 - 1000 = 200N
Resultant force = 200N to the left - the object is going backwards
If a resultant force moves an object, what happens?
Work is done.
When a force moves an object through a distance, energy is transferred and work is done on the object
What does the force do in order move an object?
It does work. It needs a source of energy to do this, like fuel or food. Energy gets transferred from one store to another
What is the calculation for work done?
Work done = Force x distance
J = N x m
What is the difference between energy transferred and work done?
There is none