Transcript Motion
ICP TCHS “Motion” Students who demonstrate understanding can: Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration. [Clarification Statement: Examples of data will include tables or HSgraphs of position or velocity as a function of time PS2-1. for objects subject to a net unbalanced force, such as a falling object, an object rolling down a ramp, or a moving object being pulled by a constant force.] [Assessment Boundary: Assessment is limited to one-dimensional motion and to macroscopic objects moving at non-relativistic speeds.] What is motion? motion - a constant change in position distance - the result of motion in any direction displacement - the result of motion in a particular direction(sign indicates direction) scalar - a quantity having magnitude only vector - a quantity having magnitude and direction Speed or Velocity? speed - the time rate of change in distance velocity - the time rate of change in displacement Speed is a scalar. Why? Velocity is a vector. Why? For now, we will use the terms speed and velocity without regard to direction. Sample Problem Suppose you drive 30 miles in 0.5 hours. What is your average speed in mi/hr? ft/s? How did you estimate your answer to the first part of the question? How can you calculate the answer to the second part of the question? Page 72, Practice Problems 1,2 in notes Acceleration acceleration - the time rate of change in velocity a = (vf - vi ) / t A car moving at 25m/s increases to 55m/s in 5 seconds. Find its rate of acceleration. a = (55m/s - 25m/s)/5s = (30m/s)/5s = 6m/s2 What does negative acceleration indicate? Experiment You will roll a ball down an incline and measure the time required for it to roll 0-10cm, 0-20cm, etc up to 0-100cm. Make three trials and average each. Record all average values in a data table. Plot a graph of x vs t. Analyze the graphs with regards to constant and varying slopes. Write a report for this experiment. 2-3 Falling Objects When gravity acts on an object, the object is accelerated at the rate of 9.8m/s2, 980cm/s2 , or 32ft/s2. These numbers are constant and should be memorized. Any time free fall is involved, a in an equation should be replaced with g, the acceleration due to gravity. Page 80, 1-7 Lab Report Format 40 pts-due next class meeting after lab is completed Upon completion of each experiment, you will turn in a lab report using the following format. The report will be referred to as a ppoc. p - Purpose - usually one statement p - Procedure - steps which will duplicate what you have done, you may use diagrams o - Observation - includes data (use data table when possible) and calculations c - Conclusion - what you learned, possible reasons for error, suggestions for improvement and opinion Experiment You will roll a golf ball down an incline and measure the time required for it to roll 0-10cm, 020cm, etc up to 0-100cm. Make three trials and average each. Record all average values in a data table. Plot a graph of x vs t. Plot a graph of v vs t. Analyze the graphs with regards to constant and varying slopes. Write a lab report for this experiment. Plotting Graphs 1. Identify the independent and dependent variables. 2. Choose the appropriate range and plot the independent variable values on the x-axis and dependent on the y-axis. 3. Decide if the origin is an appropriate point. 4. Number and label the horizontal axis. 5. Repeat steps 2-4 for the dependent variable. 6. After plotting all points, draw the best fitting line through as many points as possible. 7. Give the graph a title that best describes what it represents. Content Terms Vocabulary motion distance displacement speed velocity acceleration scalar vector