Forces & Forces & FrictionFriction

Chapter 10.1 and 10.2Chapter 10.1 and 10.2

FORCE & NET FORCEFORCE & NET FORCE FORCEFORCE is a push or pull is a push or pull

on an objecton an objectDescribed by the Described by the magnitudemagnitude and and directiondirection in which it acts. in which it acts.SI Unit = NewtonSI Unit = Newton

NET FORCENET FORCE is the is the total/cumulative force on total/cumulative force on an object (add the two an object (add the two forces)forces)

Unbalanced & Balanced Unbalanced & Balanced ForcesForces

Unbalanced ForceUnbalanced Force::Causes an object to stop moving or Causes an object to stop moving or change direction.change direction.Result in a net force and Result in a net force and cause a cause a change in the object’s velocity change in the object’s velocity (motion)(motion)

Balanced ForceBalanced Force::Forces in Forces in equal magnitudeequal magnitude & & opposite opposite direction.direction.No movement / No change in velocityNo movement / No change in velocity

Why are these examples of

unbalanced forces?

What is the Net Force for the green speed racer?

What is the Net Force for the red airplane?

Can you see the unbalanced force here?

BRAIN BREAK!BRAIN BREAK!With your partner, discuss how With your partner, discuss how balanced and unbalanced forces balanced and unbalanced forces

can apply to an arm wrestling can apply to an arm wrestling match.match.

FRICTIONFRICTION FRICTIONFRICTION is a force that two surfaces is a force that two surfaces

exert on each other when they rub exert on each other when they rub against each otheragainst each otherForces act in Forces act in OPPOSITEOPPOSITE directions directions to each other!to each other!

The The strengthstrength of friction depends on of friction depends on 1) the type of surface1) the type of surface 2) how hard the surfaces push each 2) how hard the surfaces push each

other.other.

Types of FrictionTypes of Friction1) Static Friction (Strongest)1) Static Friction (Strongest)

Acts on objects that are not moving. Works in Acts on objects that are not moving. Works in opposite direction to intended motion.opposite direction to intended motion.

2) Sliding Friction2) Sliding FrictionOccurs when two solid surfaces slide over each Occurs when two solid surfaces slide over each other. other.

3) Rolling Friction3) Rolling FrictionOccurs when an object rolls over a surface. Occurs when an object rolls over a surface. Works in direction opposite to intended motion.Works in direction opposite to intended motion.

4) Fluid Friction (Weakest)4) Fluid Friction (Weakest)Occurs when a solid object moves through a Occurs when a solid object moves through a fluid (water, air, oil) fluid (water, air, oil)

What kind of Friction?What kind of Friction?

What kind of friction?What kind of friction?

What kind of friction?What kind of friction?

Which type of hockey has more friction?

Which skater will experience the most friction?Hint: Who exerts more downward force?