Forces and their interactions Flashcards
What are the types of quantities?
Scalar quantity
Vector quantity
What is a scalar quantity?
Physical quantities that have size (magnitude), but no specific direction
What are some examples of scalar quantities?
Speed Distance Time Mass Energy Power Density Temperature
What is a vector quantity?
Physical quantities that have direction; they have both magnitude and direction
What are some examples of vector quantities?
Acceleration Force Velocity Momentum Weight Gravitational field strength Displacement
How are vectors represented?
Using an arrow
The length of the arrow = the magnitude of the vector
The direction of the arrow = the direction of the vector
What is displacement?
Distance in a given direction
What is velocity?
Speed in a given direction
What is the difference between acceleration and velocity?
Velocity is the rate of change of displacement. Acceleration is the rate of change of velocity.
Why is acceleration and velocity a vector quantity?
Velocity is a vector quantity because it consists of both magnitude and direction. Acceleration is also a vector quantity as it is just the rate of change of velocity.
What is a force?
A push or a pull that acts on an object due to the interaction with another object
What are the types of forces?
Contact force
Non-contact force
What is a contact force?
A force which acts between objects that are physically touching
What are some examples of contact forces?
Friction
Air resistance
Tension
Reaction force
What is a non-contact force?
A force which acts at a distance, without any contact between bodies, due to the action of a field
What are some examples of a non-contact force?
Gravitational force
Electrostatic force
Magnetic force
What is Newton’s Third Law of Motion?
When two objects interact with each other, they exert equal and opposite forces on each other
What is Newton’s First Law of Motion?
If no resultant force acts, an object will remain stationary or move at a constant speed in the same direction
What is Newton’s Second Law of Motion?
When a resultant force acts on an object, it produces an acceleration (or deceleration)
What is magnitude?
Is the size or extent of something
What is the resultant force if two unequal forces in opposite directions act on an object?
Equal to the difference between the two forces
In the direction of the larger force
What are force pairs?
When a force is exerted on each object due to an interaction between two objects
What is an example of a force pair?
The tension force exerted along a cable to a suspended object is opposed by the force of the weight of the object
What is the centre of mass of an object?
The point through which the weight of an object acts
How is the centre of mass of an irregular object found?
by locating its balance point
What is the equation for weight?
w = mg
What will happen in absence of air resistance?
all bodies near the Earth will fall with the same acceleration regardless of their mass
What is resultant force?
Resultant force is a single force that describes all of the forces operating on a body
What does the resultant force determine?
The direction in which the object will move as a result of all of the forces
The magnitude of the final force experienced by the object
What can forces combine to produce?
Balanced forces
Unbalanced forces
What is a balanced force?
Balanced forces mean that the forces cancel each other out and no resultant force acts on the body
What is an unbalanced force?
Unbalanced forces mean that the forces do not cancel out completely and there is a resultant force on the object
What is the equation for resultant force?
f = ma
What is tension?
The force experienced by a cable, rope, or string when pulled, hung, rotated or supported
What is a normal contact force (reaction force)?
The force arising when an object rests against another object - that is acting at a 90° angle to the plane of contact
What is upthrust?
The upward buoyancy force acting on an object when it is in a fluid
What is friction?
The force that arises when two surfaces are in contact with each other
What are free body diagrams used for?
to show the various forces acting on objects
How do you find the energy stored for an elastic band on a graph?
calculate the area under the graph
What is the parallelogram of forces used to find?
the resultant force of two forces that do not act along the same line
How do you find the scale when finding the resolution of forces?
vector value / vector length (cm)
How can an object be at equilibrium?
The resultant force on the object is zero
The forces acting on the object have no overall turning effect
How can you determine if an object is at equilibrium?
if forces are parallel - the sum of force in one direction must be equal to the sum of force in another direction (resultant force is 0)
if forces are perpendicular - the component on each line must balance out if the resultant force is 0
equation linking force, spring constant and extension?
force (f) = spring constant (k) x extension (e)
What makes an object elastic?
if it returns to its original shape when the forces deforming it have been removed
When is the relationship linear between the extension of a spring and the force applied?
The extension of a spring is directly proportional to the force applied to it, as long as the limit of proportionality is not exceeded.
When is the relationship non-linear between the extension of a spring and the force applied?
Beyond the limit of proportionality, the extension of a spring is no longer proportional to the force applied to it.
What is Hooke’s law?
fst
equation for acceleration?
acceleration = change in velocity / change in time
What are the factors affecting the centripetal force?
mass of the object
its speed
the radius of the circle
