Introduction to solving acceleration problems

Transcription

1 Introduction to solving acceleration problems

2 We learned previously that speed is a function of distance and time: s = d t We also learned that velocity is a nearly identical formula. The difference is that velocity is a function of displacement and time. Since displacement is a vector (has a direction), then velocity is also a vector. v = d t

3 The formula for acceleration is also similar. Acceleration is a function of velocity and time: a = Δv In order to find acceleration, you must first calculate the change in velocity. Subtract the initial velocity from the final velocity: Δv = v final v initial t

4 A car at a stop sign accelerates to a final velocity of 30 m/s. If it takes 10 seconds for the car to reach it s final velocity, what is its acceleration? STEP 1: WRITE DOWN ALL OF THE INFORMATION THE PROBLEM GIVES YOU! a =? That what it s asking Final velocity =? 30 m/s Initial velocity =? 0 m/s t =? 10 seconds

5 A car at a stop sign accelerates to a final velocity of 30 m/s. If it takes 10 seconds for the car to reach it s final velocity, what is its acceleration? STEP 2: CALCULATE V Δv = v final v initial Δv = 30 m s 0 m s Δv = 30 m s

6 A car at a stop sign accelerates to a final velocity of 30 m/s. If it takes 10 seconds for the car to reach it s final velocity, what is its acceleration? STEP 3: PLUG NUMBERS INTO THE FORMULA a = Δv t a = 30 m s 10s

7 A car at a stop sign accelerates to a final velocity of 30 m/s. If it takes 10 seconds for the car to reach it s final velocity, what is its acceleration? STEP 4: SOLVE THE NUMBERS = 3

8 A car at a stop sign accelerates to a final velocity of 30 m/s. If it takes 10 seconds for the car to reach it s final velocity, what is its acceleration? STEP 5: SOLVE THE UNITS m s s = m s 1 s m s 1 s = m s 2

9 A car at a stop sign accelerates to a final velocity of 30 m/s. If it takes 10 seconds for the car to reach it s final velocity, what is its acceleration? STEP 6 = PUT NUMBERS AND UNITS TOGETHER. DOES IT MATCH WHAT YOU WERE ORIGINALLY LOOKING FOR? a = 3 m s 2 Down the road DO WE MEASURE ACCELERATION WITH M/S 2? Yes! Problem solved.

10 The world s fastest train set its speed record in If it takes15 minutes for the TGV to reach 575 km/h, what is its acceleration( in m/s 2 )? STEP 1: WRITE DOWN ALL OF THE INFORMATION THE PROBLEM GIVES YOU! a =? That what it s asking Final velocity =? 575 km/h Initial velocity =? 0 m/s t =? 15 minutes

11 The world s fastest train set its speed record in If it takes15 minutes for the TGV to reach 575 km/h, what is its acceleration( in m/s 2 )? STEP 1A: CONVERT THE GIVEN INFORMATION TO THE UNITS WE NEED. Final velocity is given in km/h. We need meters per second. 575 km/h = 575,000 m/h 575,000 m/h 60 (mintues) 60 (seconds) = 160 m/s

12 The world s fastest train set its speed record in If it takes15 minutes for the TGV to reach 575 km/h, what is its acceleration( in m/s 2 )? STEP 1A: CONVERT THE GIVEN INFORMATION TO THE UNITS WE NEED. Time is given in minutes. We need seconds. 15 minutes 60 seconds per minute = 900 seconds

13 The world s fastest train set its speed record in If it takes15 minutes for the TGV to reach 575 km/h, what is its acceleration( in m/s 2 )? STEP 2: CALCULATE V Δv = v final v initial Δv =160 m s 0 m s Δv =160 m s

14 The world s fastest train set its speed record in If it takes15 minutes for the TGV to reach 575 km/h, what is its acceleration( in m/s 2 )? STEP 3: PLUG NUMBERS INTO THE FORMULA a = Δv t a = 160 m s 900s

15 The world s fastest train set its speed record in If it takes15 minutes for the TGV to reach 575 km/h, what is its acceleration( in m/s 2 )? STEP 4: SOLVE THE NUMBERS = 0.17 Round your answer to 0.18

16 The world s fastest train set its speed record in If it takes15 minutes for the TGV to reach 575 km/h, what is its acceleration( in m/s 2 )? STEP 5: SOLVE THE UNITS m s s = m s 1 s m s 1 s = m s 2

17 The world s fastest train set its speed record in If it takes15 minutes for the TGV to reach 575 km/h, what is its acceleration( in m/s)? STEP 6 = PUT NUMBERS AND UNITS TOGETHER. DOES IT MATCH WHAT YOU WERE ORIGINALLY LOOKING FOR? a = 0.18 m s 2 Along the tracks DO WE MEASURE ACCELERATION WITH M/S 2? Yes! Problem solved.

18 Open your books to p. 58. Attempt problems 22, 23, and 24. We will use the clickers to see how well you are doing. Honors: Use p Attempt problems 1-5. We will use the clickers to see how well you are doing.