Forces Flashcards
What are the three properties of a force
Magnitude
Point of application
Direction
What are the two components of direction
Line of action
Sense
What do you need to fully describe a force?
Its size and direction
Define direction
the way the force is applied
(arrow head)
Define magnitude
The size of the applied force (length)
Define point of application
The point at which the system receives the applied force
Define line of action
The imaginary line extending indefinitely along the vector through the tip and tail (shaft)
What is a contact force
The result of physical contact between two bodies
What can be classified as contact or non-contact forces
External forces
T/F Force is directly proportional to mass
True
What type of force is someone pushing on a desk
Action force
What type of force is a desk “pushing back” on someone pushing it
A reaction force
What is newtons third law?
Forces come in pairs, with every action there is an equal and opposite reaction
Describe the forces when someone jumps in the air
The person pushing on the ground is the action force. The ground pushing the person up into the air is the reaction force.
Describe external forces
They interact with the system from the outside
Only external forces can change the motion of a system
Describe internal forces
They act within the defined system
Only internal forces can change the shape of the system
Is the floor an internal or external force when someone is walking
External
Define a motive force
A force that tends to lead to a change in motion in the form of increased velocity or change in direction of the system
Define a resistive force
A resistive force tends to prevent changes in motion by other external forces or decrease the velocity of a system that is already in motion
Describe the forces when someone is skydiving
Gravity is the motive force and air resistance is the resistive force
T/F if a force tends to lead to a change of motion in the form of increased velocity of the system, then the force is resitive
False, the force is motive
Where is gravitational pull concentrated
At the center of mass
What type of force is gravity
Non-contact
Active
External
Define static friction
It is when two contacting surfaces are not currently sliding relative to each other but do possess the potential for movement
Define kinetic friction
It is when the two contacting surfaces are already sliding relative to each other
Define rolling friction
When one surface is rolling over another but not sliding
Which type of friction coefficient is the strongest in decreasing order
Static > dynamic (kinetic) > rolling
What is limiting friction
The maximum friction that you can get from the ground to counter external force
Give an example of motive friction
The friction of your foot and the ground when you walk
What does the complexity of vector composition depend on
The number of vectors and the relative directions and orientations of the vectors
What is vector resolution
The process used to resolve a single vector into its individual directional component vectors
