Name __________________________________ Block _________________________________ Lab: Catch It MYP Physics Purpose: To explore freefall and understand uncertainty in measurements. Procedure: You will be calculating your reaction time by using what you know about acceleration due to gravity. Reaction time is the time elapsed between a stimulus and your response. A stimulus for this experiment would be seeing (or hearing) a meter stick being dropped and a response would be you grabbing it. Reaction time using sight 1. Have your lab partner hold a meter stick between your fingers with the 0 m mark lined up with your fingers. Try to catch the meter stick as soon as you see your partner drop it. The person dropping the meterstick must not give any indication that he/she is about to drop it (i.e. no countdown or ready-set-go) 2. The mark where you catch the meter stick is the displacement of the fall. Record your displacements for three separate trials. Each person must calculate his/her own reaction times. 3. Solve for the amount of time (t) for which the meterstick was falling. Show all your work below for one of your trials to find the time in the space to the right of the table. 4. Calculate your average reaction time for sight. Trial Displacement of meterstick Time 1 Δx = vo = 2 vf = 3 a= Average Reaction Time = t= Reaction time for hearing 1. Repeat the above experiment only this time have your eyes closed and have your partner say “now” as they drop the meter stick. The person dropping the meterstick must not give any indication that he/she is about to drop it (i.e. no countdown or ready-set-go). Perform three trials and average the three times. Show all your work below for one of your trials to find the time. Calculate your average reaction time for hearing. Trial Displacement of meterstick 1 2 3 Average Reaction Time = Time Name __________________________________ Block _________________________________ Lab: Catch It MYP Physics Analysis: 1. What are at least two possible sources of error that might explain why you didn’t always catch the meterstick at the same spot every time? Be specific. 2. Suppose the times listed below were the results of you timing a car driving 300 meters (broken up into 100 m segments). If you compared the speed of the car in each 100 meter segment and taking into account your reaction time, do you think that the car was: getting faster each trial, getting slower each trial, or going about the same speed each trial? Explain your answer clearly. 1st 100 m: 6.21 sec 2nd 100 m: 6.28 sec 3rd 100 m: 6.32 sec 3. If you measured the time for a ball to roll down a ramp to be 10.45 s in one trial and your measured it to be 10.37 s in a second trial, could you confidently conclude that it was moving faster in the second trial? Explain. 4. You are performing a lab of timing a ball roll down a hill. You start your stopwatch when you see your partner release the ball and stop it when it gets to the bottom of the ramp. How do you think you could possibly reduce the error due to your reaction time involved in the measurement (using only a stopwatch...no other equipment)? Explain.
