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Physics Unit Test Study Guide 2012-2013

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Physics Review for Unit Test 1. Speed & Ticker Tapes 2. Acceleration and Accelerometers 3. Stride Frequency 4. Launch Angles 5. Free Fall 6. Extrapolation 7. Potential & Kinetic Energy 8. Newton’s Laws

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Speed & Ticker Tapes What is the definition of speed? Speed is the measure of how fast something moves through a particular distance over a time period. What is the formula to calculate speed? Speed = distance / time Jim Bob drinks 5 red bulls and runs the 100 m race in 6.1 seconds. Calculate his speed. Speed = distance / time Speed = 100 m / 6.1 s Speed = 16.39 m/s At the 50 meter mark in the above race do you think the elapsed time was less than, equal to, or more then 3.05 seconds? Why? Explain your answer! At the 50 meter mark, the elapsed time will be more than 3.05 seconds. It takes more time to run the first half of the race because you are starting from 0.

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Speed & Ticker Tapes Explain the terms, top speed, average speed and final speed. Top speed is the highest speed overall, at any time during the race. Average speed is the distance of the whole race / time of the whole race Final speed is the speed during the last interval of the race. Who wins the race, the runner with the highest finishing speed, average speed, and top speed? WHY? The runner with the highest average speed will win because they are able to maintain their speed over a long period of time.

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Speed & Ticker Tapes Make a ticker tape showing acceleration. How can you find top speed, average speed and final speed on this ticker tape? Top speed: find the one tick (distance between dots) that is largest and measure it. Average speed: measure the entire distance from the first dot to the last dot, and divide by the number of ticks. Final speed: measure the distance between the last three dots, and divide by the number of ticks (2)

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Accelerometers and Acceleration What is the definition of acceleration? The rate at which velocity changes over time. What is the formula to calculate acceleration? Acceleration = change in speed / change in time Draw at least 3 different pictures of accelerometers Constant / at rest Slowing down to the right, speeding up to the left Slowing down to the left, speeding up to the right

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Accelerometers and Acceleration If an object has an initial velocity of 40 m/s. After 2 seconds its final velocity is 60 m/s. What is the rate of acceleration for the object? Acceleration = change in speed / change in time Acceleration = 20 m/s / 2 seconds Acceleration = 10 m/s 2

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Stride Frequency How do you find stride frequency? Stride Frequency = Number of strides / Time (s) How do you find speed using stride frequency? Speed = Stride Frequency x Stride Length Miley jogs for 20 seconds. Her average stride length is.75 meters. She takes 50 strides. Calculate her speed! Stride Frequency = 50 strides / 20 seconds. Stride Frequency = 2.5 strides / second Speed = Stride Frequency x Stride Length Speed = 2.5 strides/second x 0.75 m Speed = 1.875 m/s Explain the effect on a runners speed if he attempts to double his stride length and cut his stride frequency in half. If the runner doubles his stride length and cuts his stride frequency in half, he will have the same speed. To change his speed, he would need to either double his stride length (increase), or cut his stride frequency in half (decrease).

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Launch Angles Define projectile, trajectory and free fall. Projectile: A fired, thrown, or otherwise propelled object. Trajectory: The path of a projectile or other moving body through space. Free fall: The fall of an object such that the only force acting upon it is that of gravity. Explain what a launch angle is. A launch angle is the the initial elevation angle of an object with respect to the ground before it is propelled. Explain what range is Range is the distance covered by an object. If the launching and landing heights for a projectile are equal what angle produces the greatest range? The angle that will create the greatest range is 45 degrees. For a constant launch speed, what angle produces the same range as a launch angle of 40 degrees? The complementary angle of 50 degrees will produce the same range.

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Free Fall Explain V=gt Velocity of Free Fall = Acceleration due to Gravity x Time Explain d = 1/2g x t 2 Distance of Free Fall = 1/2 x Acceleration due to Gravity x Time 2 If you drop a ball what is the velocity of the ball after 4 seconds? V = gt V= 10 m/s 2 x 4 s V = 40 m/s Draw a diagram showing how a ball thrown would fall off the path it wants to take in the absence of gravity from 1-5 seconds. If you drop a cannon ball off a cliff how far has it fallen in 2 seconds? d = 1/2g x t 2 D = 1/2 x 10 m/s x 2 2 D= 20 m

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Extrapolation What is extrapolation? Using historical data to try to determine what will happen in the future.

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Energy Define Potential and Kinetic Energy Potential Energy: Energy stored within an object. Kinetic Energy: Energy an object possesses due to its motion. When released potential energy turns into what? When released, potential energy turns into kinetic energy. If a raised object has 50 joules of potential energy, how many joules of potential energy will it have half way through its fall? Halfway through its fall, it will have 25 joules of potential energy.

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Newton’s Laws of Motion What are Newton’s 3 Laws? Newton’s First Law: Objects at rest remain at rest, and objects in motion remain in motion with the same velocity, unless acted on by an unbalanced force. Newton’s Second Law: the acceleration of an object increased with increased force and decreases with increased mass. (force = mass x acceleration) Newton’s Third Law: Every time one object exerts a force on another object, the second object exerts a force that is equal in size and opposite in direction back on the first object. What is Inertia? Inertia is the resistance of an object to a change in the speed or the direction of its motion. Which one of Newton’s 3 laws applies to Inertia? Newton’s First law is also called the law of inertia.

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