Section 2 Acceleration

 Students will learned about  Describing acceleration  Apply kinematic equations to calculate distance, time, or velocity under conditions of constant acceleration.

 What is acceleration? Answer: Is the rate at which velocity changes over time; an object accelerates if its speed, direction, or both change.

 Acceleration has direction and magnitude. Thus, acceleration is a vector quantity.  The units of acceleration are meters per second squared.

 A skater increases her velocity from 2 m/s to 10 m/s in 30 seconds. What is the skater’s acceleration?

Do problems from worksheet 1,2 and4

 The slope of the velocity-time graph is the average acceleration. –When the velocity in the positive direction is increasing, the acceleration is positive, as at A. –When the velocity is constant, there is no acceleration, as at B. –When the velocity in the positive direction is decreasing, the acceleration is negative, as at C.

 When velocity changes by the same amount during each time interval, acceleration is constant.  The relationships between displacement, time, velocity, and constant acceleration are expressed by the equations shown on the next slide. These equations apply to any object moving with constant acceleration.  These equations use the following symbols:  x = displacement v i = initial velocity v f = final velocity  t = time interval

 A racing car reaches a speed of 42 m/s. If then begins a uniform negative acceleration, using its parachute and braking system, and comes to rest 5.5 seconds later. Find the distance that the car travels during braking.

 A car accelerates uniformly from rest to a speed of 6.6 m/s in 6.5 s. Find the distance the car travels during this time.

 Do problems 2-4 from page 49

 Do 2-4 page 51

Final Velocity After Any Displacement A person pushing a stroller starts from rest, uniformly accelerating at a rate of m/s 2. What is the velocity of the stroller after it has traveled 4.75 m?

 Do problems from student practice  Problems 1-6 from page 54

 Today we saw about acceleration and how we can find it.  Next class we are going to continue with falling objects.