Figuring Out FCAT Physics

Figuring Out FCAT Physics

Ms. Donohue

Most of it is stuff you already know…

• Algebra…• Y= mx + b

– What is this?– b is our y-intercept – m is our slope– What is slope???

• Noooo…not that kind

• The math kind…• Slope (m) is equal

to…• Rise Run• m= (y2-y1)

(x2 – x1)

• Slopes show relationships between the axes

Find the Slope of this Line

• Pick any two points

• (0, 3) and (3, -1)

• m=rise/run• m= (y2-y1)

(x2 – x1)

• m= (3-(-1))(0 – 3)

m=-4/3

Easy right?• Any questions?• Let’s try one more…

Now the Physics…• KNOW Your UNITS!!!• Mass

– kilograms (kg)• Time

– seconds (s) • Force

– Newtons (N) which is the same as writing “kg x m/s2”

• Velocity – meters per second (m/s)

• Acceleration – meters per second squared (m/s2)

Now the Physics…• Here are the Formulas you get on the FCAT

science reference sheet– Acceleration (a)

a= Change in velocity (m/s) a= vfinal-vinitial

Time taken for the change (s) tfinal-tinitial

– Average Speed (or velocity) (v)v= Distance v= d Time t

– Force in Newtons (F)• F= mass (kg) x acceleration (m/s2) F = ma

– Work (W)• W= Force (N) x distance (m) W = Fd

We can rearrange these equations to get exactly what we are looking for

a= vf-vi

tf-ti

v= d t

F = ma

W= Fd

So how is the algebra involved in physics?

a= vf-vi

tf-ti• What does the above equation look similar to?• m= (y2-y1)

(x2 – x1)• We use this relationship to solve FCAT physics

problems….• Anytime you see a graph with a straight line, you

should think SLOPE!

Efficiency and Energy• What unit do we use to measure energy?

– Joules (J) or calorie (cal)• Percent efficiency= Energy Output x 100%

Energy InputEnergy output energy usedEnergy input energy you started with***Energy output can NEVER be greater

Other important formulas• Potential Energy

– Stored energy– Based on position of object OR

arrangement of atoms– PE= mass x gravity x height

PE=mghg always = 9.8 m/s2

• Kinetic Energy– Energy of motion– KE= mass x (velcocity) 2

2KE = m v2

2• Mechanical Energy (ME)

ME= PE + KE (super easy!)

Energy cannot be created or destroyed…it can only transferred and change form…• Hot object (lots of Energy) cold object (less energy)• Kinetic Energy changes into Potential• Light Energy (Sun) changes into Chemical Energy

(GLUCOSE molecule)

V=20 m/s

V=40 m/s

V= 0 m/s

2 m

Practice Efficiency Problems!1. Engineers make a battery that supplies iPad2’s with 16,000 J of energy

to make an output of 8,000 J of energy in the form of sound and light for the screen. How efficient is the iPad 2?

2. What is the efficiency of a hummer that uses 36,000 J of energy from gasoline to make 27,000 J of kinetic energy to move the car?

3. At Grad bash you ride The Incredible Hulk roller coaster that is 200 meters tall. The roller coaster cart has a mass of 2000kg. At the bottom of the first hill, the speed is 50 m/s. What is the efficiency of the roller coaster assuming it starts from rest at the top of the hill.

4. Hollywood Tower of Terror at MGM boasts that you will be free-falling 120 meters until you reach a speed of 6 m/s near the bottom. How efficient is the ride?

5. You are designing an Avatar roller coaster for Universal. You want to simulate the Toruks, with their deadly swoops and drops. You need to achieve a record speed of 100 m/s at the bottom of the very first drop. You meet with your fellow engineers and determine the efficiency of your sleek Toruk carts is about 85%. How high will the first hill have to be if you wanted to achieve record breaking velocity?

Answers1. 50% efficiency2. 75% efficiency3. About 64% efficiency4. About 1.5% efficiency5. About 600 meters high