MOTION & REFERENCE POINTS
What does it mean for an object to be in motion?
It changes position relative to a reference point
A push or pull
What is a force?
What are balanced forces?
Equal forces in opposite directions
Distance ÷ time
What is speed?
Change in velocity over time
What is acceleration?
An object/place used for comparison
What is a reference point?
Contact and noncontact
What are the two types of forces?
What is net force?
Total of all forces acting
Speed with direction
What is velocity?
What are two ways to accelerate?
Change speed or direction
Why is motion relative?
Because it depends on the reference point
Force that resists motion between surfaces
What is friction?
What happens when net force = 0?
No change in motion
A car travels 100 m in 20 s. Speed?
5 m/s
A car goes 0 → 20 m/s in 4 s. Acceleration?
5 m/s²
You sit in a moving car. Are you moving? Explain.
Depends—moving relative to Earth, not moving relative to car
Gravity, magnetism, electric force
What are names of three noncontact forces
What happens when forces are unbalanced?
Motion changes (acceleration)
A runner moves 60 m in 10 s east. Velocity?
6 m/s east
A bike slows from 10 m/s to 4 m/s in 3 s. Acceleration?
−2 m/s²
Give two different reference points for a flying bird.
Example: tree, ground, clouds
What do arrows represent in force diagrams?
Direction and strength
10 N right and 4 N left → net force?
6 N right
Why is 20 m/s NOT velocity?
No direction given
Can an object accelerate without speeding up?
Yes, by changing direction