This document discusses forces and motion. It defines key terms like force, net force, balanced and unbalanced forces. It explains that an object's motion can only be determined relative to another object used as a reference point. Forces can be added or subtracted depending on whether they act in the same or opposite directions. A net force causes an object to change its motion, such as starting to move, stopping, or changing direction. Balanced forces in opposite directions do not change an object's motion.

2. When an objectWhen an object’s distance from another’s distance from another
object is changing.object is changing.
You must have aYou must have a reference pointreference point inin
order to determine if something is inorder to determine if something is in
motion.motion.

3. Does the sunDoes the sun
movemove
or the Earth?or the Earth?Don’t copy
this slide.

4. TheThe pushpush oror pullpull on anon an
object.object.

5. Force between surfaces thatForce between surfaces that
resists the movementresists the movement of oneof one
surface past another surface.surface past another surface.

6. Friction also existsFriction also exists
between an object rollingbetween an object rolling
across another surface.across another surface.

7. ForceForce oror attractionattraction
between twobetween two
objects.objects.

8. Gravity and Motion
• The gravitational
constant is 9.8 m/s².
• Objects fall to Earth
at the same
acceleration
regardless of mass.

9. Measure of the force ofMeasure of the force of
attraction between anattraction between an
objectobject andand EarthEarth..
AA NewtonNewton is the metric unitis the metric unit
used to measure weight.used to measure weight.

10. Many forces act together on anMany forces act together on an
object.object.
However, it is not alwaysHowever, it is not always
easy to determine whateasy to determine what
is exerting a force oris exerting a force or
what is receiving a force.what is receiving a force.

11. When forces are applied in theWhen forces are applied in the samesame
direction, the forces aredirection, the forces are addedadded togethertogether..
Example: paddling a boat in the sameExample: paddling a boat in the same
direction helps the boat to go faster.direction helps the boat to go faster.

13. When forces are applied inWhen forces are applied in
oppositeopposite directions, subtractdirections, subtract
the smaller force to determinethe smaller force to determine
the direction.the direction.
Example:Example: tug-of-wartug-of-war

14. The resulting force is calledThe resulting force is called
thethe net forcenet force..

16. When a net force acts on anWhen a net force acts on an
object, the forces areobject, the forces are
unbalancedunbalanced..
This causes an object to startThis causes an object to start
movingmoving, stop, stop movingmoving, or change, or change
directiondirection..

17. Equal forces on an object inEqual forces on an object in
opposite directions are calledopposite directions are called
balancedbalanced forcesforces..
This does not change anThis does not change an
objectobject’s motion.’s motion.