1-D movement

Significant Figures 1. Non-Zero digits are always significant 2. Any zeros between two significant digits are significant 3. A final zero or trailing zeros in decimal portion are significant

Adding / Subtracting Count number of sig figs in decimal portion of each number Find one with lowest number Add/ Subtract as normal Round to least number of places in decimal portion

Multiplication and Division Recognize the number with lowest sig figs Multiple/ division as normal Round to the lowest number of sig figs

Practice Problems A B C. 50 pies D E *234.3

Answers A  4 sig figs B  3 sig figs C. 50 pies  2 sig figs (is an exact number, don’t round) D  1 sig figs in decimal  E *234.3  2 sig figs  834

Trigonometry SOH-CAH-TOA Sin = opposite / hypotenuse Cos= Adjacent / hypotenuse Tan = opposite / adjacent Pythagorean Theorem: h^2 = Ho^2 + Ha^2

Practice Fred is practicing shooting at the range. Fred is standing 50 meters away from his target. When Fred shoots at an angle of 10 degrees, he hits the bottom of the target, but then when he shots at an angle of 4 degrees, he hits the top of the target. At what angle does he have to shoot to hit the middle of the target, if the target is a square. (HINT: Draw a picture)

Answer: 1st find the different between the two heights 50Tan(10) – 50 Tan(4) = 5.32…. To find center, divide in half =2.666 M to the middle of target from the bottom/top Degrees = Tan ^-1 (2.66/50) = 2.7 angles

Concept Check You and your dog go for a walk to the park. On the way, your dog takes many side trips to chase squirrels. When you arrive at the park…. (which statement in correct) a) Average speed and average velocity were both different b) Average speed was the same, but average velocity was different c) Average speed was different, but average velocity was the same d) Average speed and average velocity were the same

Answer: C- average speed was different, but average velocity was the same Why? Your dog travelled more distance than you in the same amount of time, so average speed was greater Your displacements were the same though, so average velocity was the same

The graph of postion vs. tie for a car is given below. What can you say about the velocity? a) It speeds up all the time b) It slows down all the time c) It moves at constant velocity d) Sometimes it speeds up and sometimes it slows down t x

B- it slows down all the time The slope of x vs T is velocity The slope is decreasing, meaning the car is slowing down t

1 – D Kinematical Eqations For these to be true, ACCELERATION HAS TO BE CONSTANT! What are the four equations?

Problem A car accelerations from rest at 4.6 m.s^2, and acceleration at that rate for the first 20 seconds, and then does acceleration again. What is her Velocity at 20 seconds? After?

Answer: V final = v initial + at V final = o + (4.6)(20) V final = 92 m/s  if never changes accelerates or deaccelerates again, will continue at the same velocity

Problem: You throw your physics text book down the stairs. The book falls down five floors. You estimate that the book fell down 100 m. If you released the book from rest, how long did it take to hit the ground?

Solution: Use equation: y = y0 + v0(t - t0) + ½a(t – t0)2 Accélération = gravity = = 0 + o(t) +.5(9.8)(t) ^2 Square root of [100/ (.5 *9.8)] T= 4.5 seconds