Apr. 25, 2019 You need: Clean paper (2) / pencil Warm Up: Speed Machines – take home TEST (due Friday) Forces notes WS Warm Up: Mental Math – be ready. I CAN: determine effects of friction and gravity Apr. 25, 2019

Mental Math 1.) What is 20% of 200?

Mental Math 2.) Mr.Wolfe’s speed was 4 km/hr and he ran for 4 hours. How far did he go?

Mental Math 3.) 3 + 4 x 2 =

Mental Math 4.) Write 20% as a fraction. **Be careful to reduce (or simplify).**

Mental Math 5.) 0.922 m = _____ cm *Be careful to show decimal

Energy Newton’s Laws Simple Machines Speed, velocity, acceleration Motion graphs Forces/ friction Energy Newton’s Laws Simple Machines Electrical / magnetism

Teacher March Day SWAGRRR Day Tests Start Forces TEST Weather/ Atmosphere Weather/ Atmosphere Weather/ Atmosphere Weather/ Atmosphere Weather/ Atmosphere SWAGRRR Day Weather/ Atmosphere Weather/ Atmosphere Weather/ Atmosphere Weather/ Atmosphere Weather/ Atmosphere Weather/ Atmosphere Weather/ Atmosphere Weather/ Atmosphere Weather/ Atmosphere Weather/ Atmosphere Tests Start Review Review

May 27 May 28 May 29 May 30 May 31 Science Last day of school Review

Monday… Tuesday… Speed Velocity Acceleration Instantaneous Average Constant Velocity Acceleration Independent and dependent axes Straight = constant Curved = changing Slope = speed Horizontal = no motion

Wednesday and today… How do we make an object move (create motion)? How do we make an object NOT move? What factors cause motion to be faster, slower, or in a given direction? A push or a pull…a FORCE A push or a pull…a FORCE GRAVITY…a natural FORCE toward the center of the earth

Speed Machines Will be a take home test, but still needs to be honest. No help. Calculators are okay. Front and back. Show formula and work. I will collect it on Friday at the beginning of class. It will be considered a test grade.

FAST vs. SLOW FAST SLOW

Starting & Stopping

No Motion

Speeding Up Acceleration Slowing down

Classwork / Homework (Thurs) Forces notes Joey’s trip – graph complete WITH A STRAIGHT EDGE!!...Turn into Ms.Garris Gravity notes (use TODAY’s ppt) Friction lab

Christy wanted to visit the zoo, which is 20 kilometers from her house Christy wanted to visit the zoo, which is 20 kilometers from her house.  To help her get there, her mother drove her to the bus stop 5 kilometers away from home and toward the zoo.  The trip took 5 minutes.  She had to wait for the bus for 5 minutes.  Christy was reading on the bus and missed her stop.  She finally got off the bus 10 minutes later at the next stop 1 kilometer past the zoo.  It took Christy 15 minutes to walk back to the zoo.

Christy wanted to visit the zoo, which is 20 kilometers from her house Christy wanted to visit the zoo, which is 20 kilometers from her house.  To help her get there, her mother drove her to the bus stop 5 kilometers away from home and toward the zoo.  The trip took 5 minutes.  She had to wait for the bus for 5 minutes.  Christy was reading on the bus and missed her stop.  She finally got off the bus 10 minutes later at the next stop 1 kilometer past the zoo.  It took Christy 15 minutes to walk back to the zoo.

& AIR RESISTANCE The physics of falling GRAVITY & AIR RESISTANCE The physics of falling

The Force of Gravity Gravity is the force that pulls all objects down to the earth. Rain falls from the sky down to earth… If you drop a book, it falls to the ground… If you trip, you’ll fall down…

Universal Gravitation Actually in science, gravity is a force of attraction that acts between ALL objects (the earth, you, the desk, a book) The force of gravity is much STRONGER for LARGER objects (more mass).

Universal Gravitation Because the Earth is by far, the largest and closest object around, it has the greatest force of attraction... So, no matter where you are on earth, all things fall to the ground due to gravity…

What is “free fall”? When gravity is the ONLY force acting on an object, it is in free fall. In that case, gravity is an UNBALANCED FORCE which causes the object to accelerate.

Acceleration due to Gravity Calculate the acceleration of an object in free fall. A = Final speed – initial speed time A = 50 m/s – 0 m/s 5 s Acceleration = 10 m/s2

Objects in Free Fall Do all objects fall at the same rate? If we dropped a bowling ball and a tennis ball from the same height, which would land first? Let’s try it!

Question: How does mass affect the speed of a falling object? Mass and Gravity Oct. 24, 2008 Question: How does mass affect the speed of a falling object? Hypothesis: (What do you think will happen AND WHY?) Observations & Data Collection: Repeat each trial twice and record your observations. Ping pong ball vs. Wooden ball: Wooden ball vs. Metal ball: Ping pong ball vs. Metal ball: Conclusion: (One sentence)

Objects in Free Fall Do all objects fall at the same rate? ALL objects in free fall travel at the same rate, regardless of mass! In free fall, heavy objects and light objects fall at the same rate!

So, which will land first? WHY does the penny land first? Remember the force that opposes motion (slows things down)? FRICTION! Falling objects experience friction with the air called AIR RESISTANCE that slows them down.

Air Resistance The larger the object (more surface area), the more air resistance. That’s why parachutes work! The upward force of the air acting on the LARGE parachute slows you down as you fall.

Air Resistance Draw a diagram showing the forces… Gravity Draw a diagram showing the forces… Downward force of gravity is same on both. Upward force of air resistance is greater on the feather. The net force (down) is greater on the penny. Net Force on Penny Net Force on Feather

Without air resistance, all objects would fall at the same rate… Galileo Drops the Ball Hammer and Feather Drop on the Moon

That’s why astronauts weigh less on the moon! Gravity on the moon? The force of gravity is much weaker on the moon because… It is much farther away from earth. The moon is much smaller than earth. That’s why astronauts weigh less on the moon!

Gravity Review Gravity is the force that pulls all objects down to the earth. When gravity is the ONLY force acting, ALL objects accelerate at a rate of 10 m/s2. Mass doesn’t matter – in free fall, heavy objects and light objects fall at the same rate!

Air Resistance Review Some objects take longer to fall – they are slowed down by FRICTION with the air called AIR RESISTANCE. The larger the surface area, the greater the force of air resistance pushing up. Without air resistance, all objects would fall at the same rate…

Draw a free body diagram of the sky diver and label ALL the forces. Gravity = 1000 N Air Resistance = 800 N What is the net force? Air Resistance = 800 N Net Force = 200 N Gravity = 1000 N

Today… Why do things move DOWN the ramp – even though you do not push/pull them? How did you make them move faster? (list three successful ways) How did you make them move more slowly? (list three successful ways) Fill in the chart about surface types. Define friction. Define gravity.

Done in class 4/17 Challenge Make a ramp (books, wooden plank, ruler) Roll the pencil (it’s Ms.Garris’s – keep it nice!) Goal: make the pencil roll down the ramp and 30 centimeters beyond the ramp. No pushing!! Done in class 4/17

Done in class 4/17 -reviewed good/bad Ramp Challenge Can you adjust to make it roll 30 centimeters? How? Describe your solution. Can you adjust to make it roll 30 cm as fast as possible? How? Describe your solution. Can you adjust to make it roll 30 cm as slowly as possible? How? Describe your solution. Done in class 4/17 -reviewed good/bad