Forces Flashcards
What are vector and scalar quantities?
Vectors have magnitude and direction
Scalars only magnitude
What are examples of vector quantities?
Force, velocity, displacement, acceleration, momentum
What are examples of scalar quantities?
Speed, distance, mass, temperature and time
How are vectors usually represented?
By an arrow, the length of the arrow shows the magnitude and the direction of the arrow shows the direction of the quantity
What is a force?
A force is a push or pull that acts on an object due to the interaction with another object
What is a contact force and examples?
When two objects have to be touching for a force to act
Friction, Air resistance, tension, normal contact force
What is a non contact force and examples
When two objects do not need to be touching for a force to act
Magnetic, gravitational, electrostatic
What is the relationship between the weight of an object and mass of an object?
The weight of an object and the mass are directly proportional
What is work done?
Work done is the energy transferred when a force moves an object through a distance
How do you convert between Joules and Nm
1J = 1Nm
What are the energy transfers when you are doing work against frictional forces?
Kinetic energy and thermal energy. The overall temperature of the object and surface starts to increase
What causes an object to stress, compress or bend?
When more than one force is acting on the object in different directions. Otherwise the object would only move in the direction of the applied force instead of changing shape
What is elastic deformation?
When an object can go back to its original shape and length after the force has been removed - elastic objects (spring)
What is inelastic deformation?
When an object doesn’t return to its original shape and length after the force has been removed
What is the relationship between the extension of an elastic object and force of an object?
The extension of an elastic object is directly proportional to the force, provided that the limit of proportionality is not exceeded
What is inertia?
The tendency of an object to remain stationary or continue travelling at a constant velocity
Provided the spring is not inelastically deformed…
the work done on the spring and the elastic potential energy stored are equal
How do you investigate springs?
- measure the natural length of the spring when no load is applied using a ruler clamped to the stand. Make sure you take the reading at eye level and add a marker to the bottom of the spring to make the reading more accurate
- add a mass to the spring and allow it come to rest. Record the mass and measure the new length of the spring. The extension is the change in length
- repeat this process until you have enough measurements
- plot a force-extension graph which will only start to curve if you exceed the limit of proportionality
What type of relationship is a straight line graph?
linear relationship, directly proportional F = ke so the gradient of the straight line is equal to k, the spring constant
What type of relationship is it when the line begins to bend?
non-liner between force and extension - the spring stretches more for each until increase in force
What is the moment?
the turning effect of a force
What is the equation for the moment?
M = Fd
M = Nm
F = N
D = perpendicular distance from the line of action of the force to the pivot
What happens if an object is balanced in terms of moment?
the clockwise moment = the anticlockwise moment about the pivto so it won’t turn
Why are levers know as force multipliers?
they reduce the amount of force that’s needed to get the same moment by increasing the distance
