P5 Flashcards
What is the difference between a scalar and vector quantity?
Scalar quantities - magnitude only
Vector quantities - have magnitude and direction
How can a vector quantity be represented?
using an arrow
- the length=magnitude
- the direction of the arrow= direction of the vector quantity
What is a force?
A push or pull that acts on an object due to their interaction with another object
What are contact forces?
The objects are physically touching
What are non-contact forces?
The objects are physically separated
Give examples of contact forces
- friction
- tension
- air resistance
Give examples of non-contact forces?
- gravity
- electrostatic force
- magnetic force
What is an interaction pair?
A pair of forces that are equal (in magnitude) and opposite in direction
Is force a scalar or vector quantity?
Vector
What is weight?
The force acting on an object due to gravity
How can you calculate the weight of an object
W= m x g
W= weight (N)
m= mass (kg)
g= gravitational field strength (N/kg)
Where does the weight of an object act?
at the object’s ‘centre of mass’
What is weight measured with?
a newton meter
Describe the relationship between the weight and mass of an object
the weight of an object is directly proportional to the mass of an object
What is the resultant force?
a number of forces acting on an object that may be replaced by a single force that has the same effect
What happens when the forces acting on an object combine to give a resultant force of 0?
The forces are balanced and the object is in equilibrium
When is work done on an object?
When a force causes an object to move through a distance (when the force causes a displacement of the object)
How can you calculate the work done by a force on an object?
W= F x s
W= work done (J)
F= force (N)
s= distance (m)
What happens when work is done against the frictional forces acting on an object?
It causes a rise in the temperature of the object
Why does more than one force have to be applied in order to change the shape of an object (by bending, stretching or compressing) ?
Otherwise the object (e.g. the string) would just move in the direction of the single applied force.
What is the difference between elastic deformation and inelastic deformation?
elastically deformed - if it can go back to its original shape and length after the force has been removed
- e.g. a spring, rubber band
inelastically deformed - if it does not return to its original shape and length after the force has been removed, its shape will have been changed permanently
Describe the extension of an elastic object
The extension of an elastic object is directly proportional to the force applied, provided that the limit of proportionality is not exceeded
What is the equation for force?
F= k x e
F= force (N)
k= spring constant (N/m)
e= extension (m)
What does a force that stretches or compress a spring do?
It does work and elastic potential energy is stored in the spring
provided the spring is not inelastically deformed, the work done and the elastic potential energy stored are equal
What is the equation used to calculate elastic potential energy (up to the limit of proportionality)?
Ee = 1/2 x k x e^2