Physics IB Assessment Review 1st six weeks Cowgill Physics is called the basic science because it is the study of unanswered questions about nature and it forms the foundation for other sciences so you can better understand them. Physical sciences include geology, astronomy, chemistry, and physics. Life sciences include biology, zoology, and botany. Physics studies motion, forces, energy, matter, heat, sound, light, and atoms. Scientific Method: Problem- what question do you want answered about something you have observed? Hypothesis- what do you think the answer might be? (an educated guess, in the form of an if-then statement…..it must be testable) Prediction-what will happen if your hypothesis is correct? Experiment-test your hypothesis Results-visually show the data you have gathered in your experiment Conclusion-was your hypothesis correct? What did you learn from the experiment? Vocabulary: Fact- a close agreement by competent observers of a series of observations of the same phenomenon Laws or Principles- a general hypothesis or statement about the relationship of natural quantities that has been tested over and over again and has not been contradicted. Theory- a synthesis of a large body of information that encompasses well-tested and verified hypotheses about certain aspects of the natural world. (Theories are based on facts) Science- deals with theoretical questions; it is a “way of knowing” Technology- deals with practical problems; it is a “way of doing” Metric Conversion: Kilo Hecta Deka Base Deci Centi Milli (Kiss Her Daily Because Divorces Cost Money) Chapter 2 Motion: When we describe something in motion, we are comparing it to something else. For example: A car is driving at 45 miles per hour – this is compared to the road and the trees around it which are standing still. Speed is a measure of how fast something is moving. The speed at any instant is called instantaneous speed. (your speedometer) Average speed = total distance/time (a trip in the car for a few hours) What is the speed of a man running 8 miles in 2 hours? Answer: 8 miles (total distance)/ 2 hours (time interval) = 4 miles/hour Remember: “per” means “every” So, 45 miles per hour is saying that something moves a distance of 45 miles EVERY hour. Velocity is speed in one direction. Constant velocity is remaining the same or staying constant. Changing velocity is not remaining the same or changing. Acceleration is changing velocity; either speeding up or slowing down. Acceleration = Change in velocity / time interval Example: A plane travels from 0 m/s to 60 m/s in 6 seconds. What is its acceleration? Answer: Change in velocity = ending velocity – beginning velocity = 60 – 0 = 60 m/s Acceleration = change in velocity / time interval = 60/6 = 10 m/s/s Acceleration always has 2 time units shown Free Fall: Why does an object fall to the ground when dropped? Gravity! Gravity pulls all objects toward earth at an acceleration of -9.8 m/s/s. (g on other planets may be different but the equations are the same) Elapsed time- the time that has passed since the beginning of the fall. In free fall, an object accelerates at a rate of 10 m per second every second. To calculate velocity in free fall, velocity = gravity x time ( v = g x t ) g = 10 To calculate distance in free fall, distance = ½ gravity x time2 (d = ½ g x t2 ) Graphing: You can graph the relationships of both time and speed (acceleration graph) and time and distance (velocity graph) by using x and y coordinates. Newtons first law: an object at rest will stay at rest and an object in motion will stay in motion unless acted upon by an unbalanced force….(an unbalanced force is something other than zero) Know the difference between speed, velocity, and acceleration Know how to calculate the velocity and distance of objects in free fall Know what “g” is Know metric converstion (Kiss Her Daily Because Divorces Cost Money) Know how to read graphs Know lab rules Know relativity of motion Be prepared to solve vectors Vf = vi + at D = vit + ½ at2 D = ½ (vf + vi)t Vf2 = vi2 + 2ad Significant figures: All non-zero digits are significant (22.2 has 3 significant digits) All zeros between two non-zero digits are significant (1007 has 4 sf) For numbers less than one, zeros directly after the decimal point are not significant (.0024 has 2 sf) A zero to the right of the decimal and following a non-zero is significant (.0500 has 3 sf) All other zeros are not significant (500 has one sf) Scientific notation allows you to give a zero significance When adding or subtracting the least number of places after the decimal is the limiting number When multiplying or dividing the number with the least sf is the limiting number Practice: 1. What 2 units of measurement are necessary for describing speed? 2. What kind of speed is registered by a speedometer? 3. What is the average speed in kilometers per hour for a horse that gallops a distance of 15km in a time of 30 min? 4. How far does a horse travel if it gallops at an average speed of 25 km/hr for 30 minutes? 5. Define speed and velocity. 6. Define acceleration 7. Review the distance-time graphs and velocity-time graphs from the fast walker, slow walker, fast start, and fast finish. 8. What is the acceleration of a car that increases its velocity from 0 to 100 km/hr in 10 seconds? 9. What is the acceleration of a car that maintains a constant velocity of 100 km/hr for 10 seconds? 10. What is the acceleration of an object in free fall 11. What equation is used for the velocity of a freely falling object? 12. What equation is used for the distance of a freely falling object? 13. What is the velocity of an object 5 seconds after it is dropped? 6 seconds after? 14. What is the distance traveled for a free falling object that is dropped from rest 5 seconds after it is dropped? 6 seconds? 15. What is the affect of air resistance on falling objects? 16. Consider the measurements: 10m, 10m/s, 10m/s/s. Which is speed or velocity, which is acceleration, and which is distance? 17. What is the acceleration of a vehicle that changes its velocity from 100 km/hr to a dead stop in 10 seconds? 18. A body with an initial velocity of 8 m/s moves with a constant acceleration and travels 640 m in 40 seconds. Find its acceleration. 19. A box slides down an inclined plane with a uniform acceleration and attains a velocity of 27 m/s in 3 seconds from rest. Find the final velocity and distance moved in 6 seconds (initially at rest). 20. A car has a uniformly accelerated motion of 5 m/s2. Find the speed acquired and distance traveled in 4 seconds from rest. 21. Before leaving the ground an airplane traveling with constant acceleration makes a run on the runway of 1800 m in 12 seconds. Find a) acceleration b) speed at which it leaves the ground c) distance traveled during the first and twelfth seconds. 22. A marble is dropped from a bridge and strikes the water in 5 seconds. Calculate the speed with which it strikes and the height of the bridge. 23. A car starts from rest and accelerates uniformly to a velocity of 80 ft/s after traveling 250 ft. Find its acceleration. 24. What velocity is attained by an object which is accelerated at 0.30 m/s2 for a distance of 50. m with a starting velocity of 0.0 m/s?