Chapter 5 - Forces Flashcards
What do vector quantities have
Vector quantities have a magnitude and direction
What do you call a physical quantity that only has magnitude and no direction
Scalar quantities
What are examples of vector quantities
Force Velocity Displacement Acceleration Momentum
What are examples of scalar quantities
Speed Distance Mask Temperature Time
What are vectors usually represented by
An arrow
The length of the arrow shows the magnitude
The direction of the arrow shows the direction of the quantity
All forces are either …
Contact on noncontact
What is a contact force
When two objects have to be touching for a force to act, that forces called a contact force
E.g. friction, air resistance
What is a noncontact force
If the objects do not need to be touching for the force to act, the force is a noncontact force
E.g. magnetic force
What is gravitational force
Gravitational forces the force of attraction between masses
What gives everything a weight
Gravity
What is the difference between weight and mass
Mass is just the amount of stuff in an object. The mass of an object will have the same value anywhere in the universe
Weight is the force acting on an object due to gravity (the pull of the gravitational force on the object). This can be different on different planets
What does the weight of an object depend upon
I depend on the strength of the gravitational field at the location of the object
What is weight measured in
Newtons
What do you measure weight with?
Newton metre
Are mass and weight directly proportional
Yes they are
How do you calculate the weight of an object if you know it’s mass and the Strength of the gravitational field
Weight = mass X gravitational field strength
How do you show all the forces acting on an object
Free body diagrams
What is a resultant force
The resultant force is the overall force on a point or object
What is an example of resultant force on the skydiver
Skydiver has more than one force acting at a single point so you can replace them with a single force which is called the resultant force. If the forces all 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
What must be done to make something move
A force must be applied
What does the thing applying the force need to move something
The thing applying the force needs a source of energy e.g. fuel or food
The force does work to move the object and the energy is transferred from one store to another
How do you work out how much work has been done if you’re given the force and distance moved along the line of action of the force
Work done = force X distance
When is one joule of work done
One jewel of work is done when a force of one Newton causes an object move a distance of 1 m
1J = 1NM
