Forces
Force
• Any push or pull on an object
• Act in pairs
• Measured in Newtons (N)
• Types of forces
– Gravity, Friction, Electrical, Magnetic, Buoyant,
Centripetal, Lift, Drag, Thrust
Force
• Every force has a magnitude and a direction
– Magnitude is the amount or size of the force
• Forces can work together or against each other
• Forces can be balanced or unbalanced
Acceleration
• Acceleration – change in speed or direction of
an object
•
•
•
•
•
Starting
Stopping
Speeding up
Slowing down
Turning
Acceleration Demonstration
• Was the car accelerating at the top of the
ramp?
• Was the car accelerating at the bottom of the
ramp?
Balanced Forces
• Occurs when there is NO CHANGE in an
object’s motion
• No acceleration = No change in motion
• Forces are balanced when objects are at rest
or traveling at a constant speed and
direction.
Balanced forces
Draw this example.
Balanced Forces
• Lets say you are
standing on the
ground. Since the
floor pushes upward
on you and gravity is
pulling down on you,
you are at
equilibrium.
Unbalanced Forces
Draw this example.
• Always cause a change in motion =
Acceleration
Check your Understanding
• Where do the balanced forces occur?
• Where do the unbalanced forces occur?
• Write them on your drawing.
Why does the toy car slow down and
stop?
Friction!
• An unbalanced force that opposes motion
between objects that are touching.
Net Force
• Combination of all forces acting on an object.
• Add forces working in the same direction.
• Subtract forces working in opposite directions.
Vectors
• Lines with arrows that show the direction of
force.
• Length of the line shows the magnitude.
Tug of War
• https://phet.colorado.edu/sims/html/forcesand-motion-basics/latest/forces-and-motionbasics_en.html
Tug of War
5N
5N - 5N = 0N
Net force = 0N
Balanced
5N
Tug of War
3N
Net force = 1N right
4N-3N=1N
Unbalanced
*Is acceleration occurring?
4N
Net force and direction
• What is the net force?
• What is the direction of
the force?
• Why?
1. Determine the Net Force and Motion
of the balloon below.
2. Determine the Net Force and motion
below.
3. Determine the Net Force and motion
below.
4. Determine the Net Force and motion
below.
5. Determine the Net Force and
motion below.
Questions?
1. What has to happen for objects to
accelerate?
– There must be an unbalanced force.
2. What are the 5 ways objects can accelerate?
– Start moving, Stop moving, Change directions,
Speed up, Slow down.