11.6 Acceleration - Review

What is acceleration A vector that changes speed or direction or both. When a object changes velocity.

What is the equation for acceleration? a = (vf – vi) / t

What does the slope of a speed-time graph tell you? acceleration

What is the value for the acceleration due to gravity? 9.8 m/s2

While traveling along a highway a driver slows from 25 m/s to 11 m/s in 12 seconds. What is the automobile’s acceleration? a = (Vf – Vi) / t a = (Vf – Vi) / t a = (11 – 25) / 12 a = ? a = -14 / 12 Vf = 11 m/s Vi = 25 m/s a = -1.167 m/s2 t = 12 sec

A parachute on a racing dragster opens and changes the speed of the car from 185 m/s to 45 m/s in a period of 4.5 seconds. What is the acceleration of the dragster? a = (Vf – Vi) / t a = (Vf – Vi) / t a = (45 – 185) / 4.5 a = ? a = -140 / 4.5 Vf = 45 m/s a = -31.11 m/s2 Vi = 185 m/s t = 4.5 sec

Describe what is occurring in each section of the speed-time graph

Describe what is occurring in each section of the speed-time graph O-A: Accelerating A-B: Constant Speed B-C: Decelerating C-D: Stopped D-E: Accelerating E-F: Constant Speed

What is the acceleration of section A? a = (Vf – Vi) / t a = (40 – 0) / 20 a = 2 m/s2

What is the acceleration of section B? a = (Vf – Vi) / t a = (40 – 40) / 30 a = 0 m/s2

What is the acceleration of section C? a = (Vf – Vi) / t a = (80 – 40) / 10 a = 4 m/s2

The cart’s acceleration is greatest during which time interval The cart’s acceleration is greatest during which time interval? (0-5 s, 5-8 s, 8-11 s, 11-16 s) 5-8 s

During how many intervals is the cart’s acceleration equal to zero?

During which time period is the cyclist moving at constant speed?

How long did it take the cyclist to reach a speed of 5 m/s?

During which time period is the cyclist speeding up (accelerating) at the slowest rate?

Which graph best represents the relationship between velocity and time for an object which accelerates uniformly for 2 seconds, then moves at a constant velocity for 1 second, and finally decelerates for 3 seconds? A

Which of these velocities vs Which of these velocities vs. time graphs above represents an object with decreasing speed? (Hint: there are 6 of them) 1,2,3,4,6,10