Forces Flashcards
What may a force cause?
A change of shape/ size to an object
What is Hooke’s Law?
The extension is directly proportional to the load beneath the elastic limit
Give the formula for Hooke’s law
Force = spring constant * Extension
F=kx
In a Hooke’s Law graph what goes on the x axis?
Load
In a Hooke’s Law graph what goes on the y axis?
Extension
How does a graph show that it obeys Hooke’s Law?
It goes through the origin and it is a straight line
How can the value of k change?
If you change the shape of the spring or the material that the spring is made out of
What is the limit of proportionality?
It is where the graph stops obeying Hooke’s Law
What can a force cause in terms of motion?
It can make an object stop, start or change direction
Define force
A push or a pull which acts upon an object as a result
Give 5 examples of forces
Frictional Force Spring force Air resistance Force Tension Force Gravitational force
What quantity is force?
Vector
State the equation for force
F=ma
What is friction?
The force exerted by two surfaces which impedes motion and results in heating
What is a form of friction?
Air resistance
What does air resistance depend on?
Velocity and Surface Area
How do you calculate the resultant force if they are in parallel?
Addition
How do you calculate the resultant force if they are in opposite directions?
Subtraction
Describe the motion states when stationary
Acceleration= zero
Resultant force= 0
Describe the motion states when an object is moving with steady velocity
Acceleration= 0
Resultant force- 0
Describe the motion states when an object is accelerating
Resultant force is NOT equal to 0
What is the force acting upon a car when going in circles?
Centripetal force
What happens to the velocity while moving in a circle?
It is always changing because of changing direction
How can you increase the centripetal force?
If the mass of the object increases
If the velocity of the object increases
If the radius of the circle decreases
What causes centripetal force?
Motion in a circular path due to a perpendicular force
Which forces may act as centripetal forces?
Friction
Gravitational Force
Tension
Normal force
What is the unit for force?
Newtons
What is the unit for spring constant?
N/m
What is a lever?
A simple machine that makes work easier to do
Give the formula for moment
Moment= f*d
What is the unit for moment?
Nm
State the equilibrium conditions
The total upward force= The total downward force
The anticlockwise moment= Clockwise moment
Give an equation for the equilibrium conditions
F1 *D1 = F2 * D2
What is the objects centre of mass?
The point where the object’s mass is most concentrated
How can you find the centre of mass?
Suspend the mass from each vertex and trace the plumb lines direction
Since the centre of mass will fall below the suspension point the centre of mass will be at the intersection of all the plump lines
What do more stable objects have?
Lower centre of gravity
Wider base
Why is a modern racing car stable?
It has a wide wheel base
A low centre of gravity
What do levers do?
Reduce the force needed to perform those tasks- they reduce the effort needed to move the load by increasing the distance over which it is acting
Define moment
A force multiplied by the perpendicular distance from the line of action of the force to the pivot
What is a scalar quantity?
Only has magnitude
What is a vector quantity
Has magnitude AND direction
Give examples of scalar quantities
Mass, speed and energy
Give examples of vector quantities
Velocity, acceleration, weight and momentum
