Force, Motion & Energy:

Newton’s 3 Laws

B. Davis & L. BlackburnMathematics & Science Center

Mass vs Weight

• Mass = measure of inertia• (resistance to change in motion)• Weight = force • (caused by gravity, affected by

both planet size and mass of body)

Mass vs Weight

• Weight in pounds• Mass in kilograms

• Mass in slugs• Weight in Newtons

Newton’s 3 Laws

• Sir Isaac Newton• Late 1600’s England• Legend of Apple• Invented Calculus• Prism and Light• Universal Law of Gravity

Phot from http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Newton.html

1st Law: Law of Inertia

• A body at rest will remain at rest• And• A body in motion will remain in

motion• Unless…

1st Law: Law of Inertia

• A body at rest will remain at rest• And• A body in motion will remain in

motion• Unless…• Acted upon by an outside force

1st Law: Law of Inertia

• Keep on keeping on

Truck and Ladder Example

Buckling Up Example

Coin Flick Example

Egg Test

Hammer example

2nd Law: Law of Acceleration

• The acceleration of a body is:• Directly proportional to force• Inversely proportional to mass

Remember: acceleration is change in speed

2nd Law: Law of Acceleration

2nd Law: Law of Acceleration

2nd Law: Law of Acceleration

Rhino example

Weight on other Planets

• Weigh in

3rd Law: Law of Reaction

•For every force on one body,

•There is an equal

• but opposite force

• on another body.

3rd Law: Law of Reaction

•For every action,

•There is an equal but opposite reaction.

3rd Law: Law of Reaction

•Forces always

•Come in pairs

•Equal in size

•Opposite in direction

•Acting on 2 different bodies

3rd Law: Law of Reaction

3rd Law: Law of Reaction

Pitched ball example

May the FORCE be with you !