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1. Physics Unit Test Study Guide

   2012-2013
2. 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
3. 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 youthink the elapsed time was lessthan, equalto, or more then 3.05 seconds? Why? Explainyouranswer! At the 50 meter mark, the elapsed time willbe more than 3.05 seconds. It takes more time to run the first half of the race becauseyou are startingfrom 0.
4. Speed & Ticker Tapes Explain the terms, top speed, average speed andfinal speed. Top speed is the highest speed overall, at any time during the race. Average speed is the distance of the wholerace / time of the wholerace Final speed is the speed during the last interval of the race. Whowins the race, the runner with the highest finishing speed, average speed, and top speed? WHY? The runner with the highestaverage speed will win becausethey are abletomaintaintheir speed over a long period of time.
5. Speed & Ticker Tapes Make a ticker tape showingacceleration. How canyoufind top speed, average speed andfinal speed on thisticker tape? Top speed: find the onetick (distancebetweendots) that is largestandmeasure it. Average speed: measure the entiredistancefrom the first dot to the last dot, anddivideby the number of ticks. Final speed: measure the distancebetween the last threedots, anddivideby the number of ticks (2)
6. Accelerometersand Acceleration What is the definition of acceleration? The rate at whichvelocity changes over time. What is the formulatocalculateacceleration? 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
7. Accelerometersand Acceleration Ifan object has aninitialvelocity of 40 m/s. After 2 secondsitsfinalvelocity is 60 m/s. What is the rate of accelerationfor the object? Acceleration = change in speed / change in time Acceleration = 20 m/s / 2 seconds Acceleration = 10 m/s2
8. StrideFrequency How do youfindstridefrequency? StrideFrequency = Number of strides / Time (s) How do youfind speed usingstridefrequency? Speed = StrideFrequency x StrideLength Mileyjogsfor 20 seconds. Her averagestridelength is .75 meters. She takes 50 strides. Calculate her speed! StrideFrequency = 50 strides / 20 seconds. StrideFrequency = 2.5 strides / second Speed = StrideFrequency x StrideLength Speed = 2.5 strides/second x 0.75 m Speed = 1.875 m/s Explain the effect on a runners speed if he attemptsto double his stridelengthand cut his stridefrequency in half. If the runner doubles his stridelengthand cuts his stridefrequency in half, he will have the same speed. Tochange his speed, he wouldneedtoeither double his stridelength (increase), or cut his stridefrequency in half (decrease).
9. LaunchAngles Defineprojectile, trajectoryand free fall. Projectile: A fired, thrown, or otherwisepropelled object. Trajectory: The path of a projectile or othermoving body throughspace. Free fall: The fall of an object suchthat the only force actinguponit is that of gravity. Explainwhat a launchangle is. A launchangle is the the initialelevationangle of an object with respect to the groundbeforeit is propelled. Explainwhat range is Range is the distancecoveredbyan object. If the launchingand landing heightsfor a projectile are equalwhatangleproduces the greatest range? The anglethatwillcreate the greatest range is 45 degrees. For a constant launch speed, whatangleproduces the same range as a launchangle of 40 degrees? The complementaryangle of 50 degreeswillproduce the same range.
10. Free Fall Explain V=gt Velocity of Free Fall = Acceleration duetoGravity x Time Explain d = 1/2g x t2 Distance of FreeFall = 1/2 x Accelerationdue to Gravity x Time2 Ifyoudrop a ballwhat is the velocity of the ballafter 4 seconds? V = gt V= 10 m/s2 x 4 s V = 40 m/s Draw a diagramshowing how a ballthrownwouldfall off the pathitwants to take in the absence of gravityfrom 1-5 seconds. If you drop a cannonball off a cliff how far has itfallen in 2 seconds? d = 1/2g x t2 D = 1/2 x 10 m/s x 22 D= 20 m
11. Extrapolation Whatis extrapolation? Usinghistorical data to try to determinewhatwillhappen in the future.
12. Energy DefinePotential and KineticEnergy PotentialEnergy: Energystoredwithin an object. KineticEnergy: Energy an objectpossesses due to its motion. Whenreleasedpotentialenergyturnsintowhat? Whenreleased, potentialenergyturnsintokineticenergy. If a raisedobject has 50 joules of potentialenergy, how many joules of potentialenergywillit have halfwaythroughitsfall? Halfwaythroughitsfall, itwill have 25 joules of potentialenergy.
13. Newton’sLaws of Motion What are Newton’s 3 Laws? Newton’s First Law: Objectsatrestremainatrest, and objects in motion remain in motion with the samevelocity, unlessacted on by an unbalanced force. Newton’s Second Law: the acceleration of an objectincreasedwithincreased force and decreaseswithincreased mass. (force = mass x acceleration) Newton’sThird Law: Every time one objectexerts a force on anotherobject, the second objectexerts a force thatisequal in size and opposite in direction back on the first object. WhatisInertia? Inertiais the resistance of an object to a change in the speed or the direction of its motion. Which one of Newton’s 3 lawsapplies to Inertia? Newton’s First lawisalsocalled the law of inertia.