N
Newton’s Three Laws
’ Th
L
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Newton’s First Law
’ Fi L
Objects at rest will stay at rest and objects in motion will stay in motion in a straight line
motion will stay in motion in a straight line unless acted upon by an unbalanced force. •Since motion remains constant unless a net pp , j
pp
force is applied, objects appear to be “_______” •Latin word for laziness: ___________
•1st Law sometimes referred to as:
Law sometimes referred to as:
Same force that causes apple to fall causes planets to stay in motion
planets to stay in motion
Unbalanced Force
N
Newton’s Third Law
’ Thi d L
• How does a cart at rest start moving?
Consider a cart moving along the ground
• Consider a cart moving along the ground
– Slows due to _________________
For every action there is always an opposite and equal reaction
and equal reaction. • Can a real cart be made to roll at constant speed?
Can a real cart be made to roll at constant speed?
• Illustration of first law with kinesthasia cart
•
•
•
•
EF 151 Spring, 2010 Lec 2‐4
3
Standing on the ground
St
di
th
d
Jumping off the ground
J
Jumping off a cart
i
ff
Air coming out of a balloon
Shooting a cannon
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Newton’s Second Law
’ S
dL
Force is equal to mass times acceleration.
Newton’s Second Law
Newton’s Third Law
R k t M ti
Rocket Motion
• First law: Unbalanced force exerted on rocket causing it to lift off from a launch pad
g
p
f = m(cannon) a(cannon)
f = m
f m(ball)
(b ll) a(ball)
(b ll)
m(cannon) a(cannon) = m(ball) a(ball)
B ild Y
Build Your Own Rocket
O R k t
Preparation:
1. Cut out all the pieces for your rocket.
Cut out all the pieces for your rocket.
• Second law: Amount of thrust (force) produced by a rocket engine determined by how fast the mass of the rocket fuel burns and the speed of the gas escaping the rocket.
2. Wrap and tape a tube of paper around the film canister Important! Place the lid end of the canister. Important!
Place the lid end of the
canister down.
• Third
Third law: The reaction, or motion, of the la The reaction or motion of the
rocket is equal to and in the opposite direction of the action, or thrust, from the engine. 3 Tape fins to your rocket body, if you wish.
3.
Tape fins to your rocket body if you wish
4. Roll the circle (with a wedge cut out) into a cone and tape it to the rocket’ss top.
cone and tape it to the rocket
top
Blasting Off
1. Put on your eye protection.
2. Turn the rocket upside down and remove the p
canister’s lid.
3. Fill the canister one‐third full of water.
Work quickly on the next steps:
Think About It!
Think About It!
1. Does the size of the tablet piece affect how long it takes for the rocket to launch?
takes for the rocket to launch?
2. Can the flight path be controlled by adding fins or a nosecone to the canister?
a nosecone to the canister?
4 Drop one‐half of an antacid tablet into the canister.
4.
Drop one half of an antacid tablet into the canister
3. How much water in the canister will give the hi h t fli ht?
highest flight?
5. Snap the lid on tight.
4. How much water will give the quickest launch?
6. Stand your rocket on a stable launch platform.
5. How would it be possible to create a two‐stage rocket?
7. Stand back and wait. Your rocket will blast off!