Newton’s LawsPhysical Science

10/15 Obj: To review 1st Law and begin 2nd

LawHW – Solve Problems

Newton’s 1st LawState the law

and draw a picture or pictures demonstrating your

understanding of the law.

Sir Isaac Newton• 1643-1727

• Lived & worked in England

• Made major developments in physics, mathematics, religion, geography, chemistry & optical science

“If I have been able to see further, it was only because I stood on

the shoulders of giants.”                        —Sir Isaac Newton

Sir Newton was born the year that Galileo died

Newton’s Laws• Newton developed three laws that govern all

motion.

• They are named Newton’s 1st,2nd, & 3rd laws.

The Law of Inertia(Newton’s 1st Law)

• Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

The Law of Inertia(Newton’s 1st Law)

• to dislodge ketchup from the bottom of a ketchup bottle, the bottle is often turned upside down, thrust downward at a high speed and then abruptly halted.

• headrests are placed in cars to prevent whiplash injuries during rear-end collisions.

• while riding a skateboard (or wagon or bicycle), you fly forward off the board when hitting a curb, a rock or another object which abruptly halts the motion of the skateboard.

Inertia• Inertia is an object’s resistance to change

Inertia

• Inertia is an object’s resistance to change

http://www.lhup.edu/gp/PhysicsClub/demo_f00_eggdrop_2_movie.mov

A note about FORCE• A force is a push or pull upon an object

resulting from the object's interaction with another object.

• Force is measured in NEWTONS (N)

• 1 Newton = 1kg * 1m/s2

• FORCE is like velocity, it has a size AND direction and can be added the same way

• The NET FORCE or FNET = total of all forces

Newtons

Newton’s 2nd Law• Objects will only accelerate if they are acted

upon by an unbalanced force

• This is shown by:

Fnet = m * a

m

F

a

F=Force

M=mass

A=acceleration

a=f÷m

m=f÷a

Newton’s 2nd Law• How much net force is required to

accelerate a 1000 kg car at 5.00 m/s2?

F = m * aF = 1000kg * 5.00m/s2

F = 5000N

Newton’s 2nd Law• What is the mass of an object that is

accelerated to 20m/s2 by 100N?

m = F / am = 100N / 20m/s2

m = 5kg

Newton’s 2nd Law

                              Because this triple-beam balance scale measures

the mass (not the weight) of an object, it will read the same on any planet.

Newton’s 2nd Law• Is an unbalanced force acting on this car?

Newton’s 2nd Law – a version• MASS is how much there is of the object

• WEIGHT is the force required to support an object against the pull of gravity

Weight = mass * gravityw = m*g

Newton’s 2nd Law• How much does a 25kg child weigh?

w = m * gw = 25kg * 10m/s2

w = 250N

Newton’s Second Law

Newton’s 3rd Law

"For every action, there is an equal and opposite reaction."

Forces always come in pairs - equal and opposite action-reaction force pairs.

Newton’s 3rd Law

Newton’s 3rd Law

A cyclist traveled at 12 km/h for 5 hours.  How far did he travel?