Acceleration Acceleration When the speed of an object

Acceleration

Acceleration When the speed of an object changes (either speeding up or slowing down)

Acceleration When the speed of an object changes (either speeding up or slowing down) *Slowing down acceleration seems odd, so we think of it as negative acceleration = deceleration.

Acceleration When the speed of an object changes (either speeding up or slowing down) *Slowing down acceleration seems odd, so we think of it as negative acceleration = deceleration. Average acceleration is a measure of how much the speed is changing every hour, minute, or second.

Acceleration Average acceleration (a) is calculated from the change of speed divided by the time taken for the change in speed to occur.

Acceleration Average acceleration (a) is calculated from the change of speed divided by the time taken for the change in speed to occur. v = change in speed t = change in time

Acceleration Average acceleration (a) is calculated from the change of speed divided by the time taken for the change in speed to occur. Acceleration = change in speed change in time

Acceleration EG – a car moving at 15 m s-1. The car speeds up to 35 m s-1 in 40 seconds. What is the average acceleration of the car?

Acceleration EG – a car moving at 15 m s-1. The car speeds up to 35 m s-1 in 40 seconds. What is the average acceleration of the car? Change in speed is v = 35 -15 = 20 m s-1

Acceleration EG – a car moving at 15 m s-1. The car speeds up to 35 m s-1 in 40 seconds. What is the average acceleration of the car? Change in speed is v = 35 -15 = 20 m s-1 Time taken = 40 s

Acceleration EG – a car moving at 15 m s-1. The car speeds up to 35 m s-1 in 40 seconds. What is the average acceleration of the car? Change in speed is v = 35 -15 = 20 m s-1 Time taken = 40 s Average acceleration = v =20 =0. 5 m s-1 t =40

Acceleration The unit for acceleration is a speed unit divided by a time unit.

Acceleration The unit for acceleration is a speed unit divided by a time unit. If the speed is in m s-1 and the time is in seconds (s), then the acceleration unit is m s-1 = m s-2 s

Acceleration The unit for acceleration is a speed unit divided by a time unit. If the speed is in m s-1 and the time is in seconds (s), then the acceleration unit is m s-1 = m s-2 s An acceleration of 5 m s-2 means that the speed is increasing by 5 m s-1 every second

Acceleration v a t

Acceleration To calculate the change in speed, use: v=a t To calculate the time taken, use: t = v a

Acceleration EG – Find the change in speed when a ball rolls down a slope, accelerating uniformly at 4. 5 m s-2 for 2 seconds

Acceleration EG – Find the change in speed when a ball rolls down a slope, accelerating uniformly at 4. 5 m s-2 for 2 seconds v=a t

Acceleration EG – Find the change in speed when a ball rolls down a slope, accelerating uniformly at 4. 5 m s-2 for 2 seconds v=a t = 4. 5 x 2 = 9 m s-1

Acceleration EG – Find the time take for a boat decelerating at 0. 3 m s-2 to change its speed from 9 m s-1 to 3 m s-1 t = v a = 9 -3 0. 3 = 20 s

Questions 1. A roller coaster car rapidly picks up speed as it rolls down a slope. As it starts down the slope, its speed is 4 m/s. But 3 seconds later, at the bottom of the slope, its speed is 22 m/s. What is its average acceleration? 2 A cyclist accelerates from 0 m/s to 8 m/s in 3 seconds. What is his acceleration ? Is this acceleration higher than that of a car which accelerates from 0 to 30 m/s in 8 seconds?

Questions 3. A car advertisement states that a certain car can accelerate from rest to 70 km/h in 7 seconds. Find the car’s average acceleration. 4. A lizard accelerates from 2 m/s to 10 m/s in 4 seconds. What is the lizard’s average acceleration?

Questions 5. A runner covers the last straight stretch of a race in 4 s. During that time, he speeds up from 5 m/s to 9 m/s. What is the runner’s acceleration in this part of the race? 6. You are traveling in a car that is moving at a velocity of 20 m/s. Suddenly, a car 10 meters in front of you slams on it’s brakes. At that moment, you also slam on your brakes and slow to 5 m/s. Calculate the acceleration if it took 2 seconds to slow your car down.

Questions 7. If a Ferrari, with an initial velocity of 10 m/s, accelerates at a rate of 50 m/s/s for 3 seconds, what will its final velocity be? 8. Falling objects drop with an average acceleration of 9. 8 m/s 2. If an object falls from a tall building, how long will it take before it reaches a speed of 49 m/s?

Questions 9. Josh rolled a bowling ball down a lane in 2. 5 s. The ball traveled at a constant acceleration of 1. 8 m/s 2 down the lane and was traveling at a speed of 7. 6 m/s by the time it reached the pins at the end of the lane. How fast was the ball going when it left Tim’s hand?

1. 2. If a ball is rolling down a hill at 6 ms-1 and speeds up to 20 ms-1 and takes 10 seconds to do this, what is the acceleration? If a dog has been let out and takes 5 seconds to get to 5 ms-1 and then speeds up to 15 ms-1 by 20 seconds, what is its acceleration?