Warm Up 99/12/11 How many significant figures are in 80900? Warms up will be checked Wed.

Test Curve was 5 points

Guaranteeing Partial Credit 1. Organize what the problem gives you 2. Make a drawing if necessary 3. Identify the equation you will use 4. Fill in the equation with the givens 5. Show your work 6. Circle your answer with the proper units

Grades Still behind in grading menus

Significant Figures and Units Are required for correct answers from now on Correct me

4 Rules to Significant Figures

Rule 1 All non-zero digits are significant. ◦ 5 m ◦ 76 m/s ◦ 4567 m/s 2 ◦ N

Rule 2 All zeroes between significant digits are also significant. ◦ 30,505 kg ◦ 50,500 s ◦ 50,000,005 m/s ◦ m

Rule 3 Zeroes to the right of a decimal or another significant digit are significant. ◦ 2.00 N ◦ J ◦ A ◦ 500.

Rule 4 Zeroes used to for spacing are NOT significant. ◦ 0.2 W ◦ V ◦ km ◦ km

When to use In problems, the least sig fig rules them all. A car can accelerate from zero to 12 m/s in 4.65 seconds. What is its average acceleration?

When to use ONLY apply significant rules to the final answer ◦ Calculators are good at being accurate A car can accelerate from zero to 12 m/s in 4.65 seconds. What is its average acceleration?

Kinematic Concepts Motion Requires a change in distance/displacement Change in distance/displacement must occur over a period of time (rate)

Difference Between Scalars and Vectors In the end, does this sailboat have a displacement?

Kinematic Concepts Average Speed Basic motion = ∆d / ∆t Speed is the rate of change of distance ◦ Speed = change in distance over time ◦ Formula: s avg = ∆distance / ∆time

Kinematic Concepts Average Velocity Basic motion = ∆d / ∆t Velocity is rate of change of displacement ◦ Velocity = change in displacement over time ◦ Formula: v avg = ∆displacement / ∆time

Difference Between Scalars and Vectors A car is going due north at 60 km/hr. Another car is going due south at 60 km/hr. Do the cars have the same speed? Do the cars have the same velocity?

Kinematic Problems Speed and Velocity An ostrich can run at speeds of up to 72 km/h. How long will it take an ostrich to run 1.5 km at this top speed?

Perfect Physics World One model of physics No friction or air resistance

Kinematic Concepts Average Velocity Motion = ∆d / ∆t Speed is the rate of change of distance Velocity is rate of change of displacement Velocity and speed tell you how fast position is changing, not just a change in position. Average velocity = ∆d / ∆t

Kinematic Vocabulary Average Velocity ◦ Can velocity be higher or lower than average over the same period of time? Instantaneous Velocity ◦ An object’s velocity at a specific moment in time Constant Velocity

Warm Up 109/13/11 Estimate the velocity the chair you are sitting on. Hint: There are at least 3 velocities.

Frame of Reference “Frame of Reference” is similar to “point of view” Motion is relative to the Frame of Reference

0 m/s 4 m/s 2 m/s 5 m/s

Your Frame of Reference is considered 0 Objects going in opposite directions – Add Objects going in the same direction - Subtract

Practice Problem What is the relative speed of 2 cars heading towards each other if one car is traveling 12 m/s and the other is 33 m/s? What is the relative speed if the fast car was trying to pass to slow car?

Kinematic Vocabulary Displacement is change in position Velocity is change in displacement over time Acceleration?

Kinematic Concepts Acceleration Acceleration is the rate of change in the magnitude AND/OR direction of velocity. Acceleration occurs when: ◦ Speed (magnitude) increases or decreases ◦ Velocity changes direction

Average Acceleration

Is there acceleration? From a dead stop, a car hits the gas and goes 100 m in 3 s. A car moves at a constant velocity of 10 m/s. Ahead, a cat starts to cross the street. The car hits the brakes! A car is driving around in a perfect circle at a constant speed.

Water drips from the ceiling at one drop per second. As the drops fall, what is their relative distance? Is the distance between 2 drops the same, increases or decreases?

How acceleration changes motion. Accel. Velocity Displace- ment t=0t=1st=2st=3st=4 s

Practice Problem A car drives for 1 hour at 20 km/h. Then it drives for 1 hour at 30 km/h. What is the average speed of the car? Did the car undergo any acceleration?

Kinematic Problems Speed and Velocity If Hawaii is 2.24 x 10 3 km long and the moves at an average speed of 50. mm per year, how many years would it take to move the length of Hawaii?

Kinematic Problems Speed and Velocity Jupiter, the largest planet in our solar system, has a radius of about 7.1 x 10 4 km. Its period of rotation, however, is only 9 h, 50 min. Calculate the average speed (in km/hr) for one rotation. What is the average velocity?