Forces Flashcards
What do we need to use to know if an object is in motion?
A reference point
Reference Point
An object that is not moving to determine if an object is moving
What is a force?
A push or pull
The SI Unit for force
Newtons
How many newtons are balanced forces?
0N
Net Force
The total or final force
What is the formula for speed?
Distance/time
The faster the object the _____ the line
Steeper
What does a horizontal line on a graph mean?
The object not moving, the slope is 0.
What does SI Stand for?
System International
The SI unit for speed
Meters per second
Instantaneous Speed
The rate something is moving at a given instant
Velocity
Speed and direction
Acceleration
Increasing speed, decreasing speed, and changing direction
What two factors does the strength of friction depend on?
How hard the surfaces push each other & the types of surfaces
Mass
The amount of matter in an object
Weight
The force of gravity on an object at the surface of planet
What two factors affect the gravitational attraction of two objects?
Mass and distance
Terminal Velocity
The greatest velocity that can be reached by an object in free fall.
Air resistance
The type of fluid friction that acts on objects as they move through a fluid
Friction
A force that opposes motion when two objects are in contact
Why are units of measurement used?
To describe an objects motion
Rate
The amount of something that occurs or changes in one unit of time
How do you find the speed for an object that’s not moving at a constant speed?
Find the average speed
How do you find the average speed?
Divide the total distance traveled by the total time
What is the formula for force?
F = Mass x Acceleration
What is the basic SI unit of length
Meters
What does the prefix “milli-“ mean?
One thousandth of the basic unit
How are Forces described?
How strong they are and in which direction they act
What part of forces are measured?
Its strength
How is the strength of a force measured?
Using the SI unit the newton
How is the Net Force found?
By combining all of the forces acting on the object
What kind of forces have a net force?
Unbalanced forces
What will unbalanced forces acting on an object do?
They can cause an object to start moving, stop moving, or change direction.
How do balanced forces affect an object’s motion?
It will not change the objects motion
What is the net force of a balanced object’s motion
0N
What are equal forces acting in opposite directions called?
Balanced forces
Friction
The force that two surfaces exert on each other when they rub against each other
Which direction does friction act?
Opposite of the object, so it causes it to come to a stop
Static friction
Acts on objects that aren’t moving
Sliding friction
occurs when solid surfaces slide over each other
Rolling friction
occurs when an object rolls over a surface
Fluid friction
Results when an object moves through a fluid - liquid or gas
What kind of friction needs the most force to overcome?
The force needed to overcome rolling friction or fluid friction is usually less than sliding friction
Free fall
When the force of gravity is an unbalanced force that causes an object to accelerate
What is acceleration near Earth’s surface due to gravity?
9.8m/s^2
What type of fluid friction is objects falling through air?
Air resistance
Is air resistance the same for all objects?
No
What makes air resistance bigger/smaller?
It increases with surface area and velocity
When does the velocity of a falling object stop increasing?
Once all forces are balanced. Air resistance increases until it’s equal to the force of gravity
Projectile
An object that is thrown.
Which way does a projectile move?
Horizontally, the force of gravity pulls it towards Earth
Who created the three laws of motion?
The English mathematician Sir Isaac Newton
What is the first law of motion?
The law of inertia
Inertia
An object’s resistance to a change in motion
What does the amount of inertia an object has depend on?
The more mass the more inertia there is, because they require a greater force to cause a change in motion
What does Newton’s second law of motion say?
Acceleration depends on the object’s mass and the net force acting on the object
What is the acceleration equation?
Acceleration = Net force/mass
How is acceleration measured?
Meters per second (m/s^2)
How do you increase acceleration?
By increasing the force. They both get larger. Also by decreasing mass
Forces are not ____
One-sided
What happens when an object exerts a force on another object?
The second object exerts a force back on the first object
What are the two forces called?
Action and reaction
What does Newton’s third law of motion say?
If one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object
Can the action and reaction be added together?
No, forces can only be added together if they are acting on the same object
