Acceleration Acceleration is how long you step on

Acceleration

• Acceleration is “how long” you step on the gas OR apply the brake • a=Δv = vf – vi Δt t Vf means velocity final Vi means velocity initial t means time The unit for acceleration is m/s/s OR m/s 2

• If acceleration is negative, this means that the object being observed is slowing down or applying the brakes.

Example 1: • A car increases it velocity from 35 km/hr to 40 km/hr in 2 seconds. What is its acceleration?

Example 2: • In 5 seconds, a car increases its velocity from 50 km/hr to 65 km/hr. While at the same time, a truck goes from rest to 15 km/hr. Which vehicle undergoes the greater acceleration?

Example 3: • A drag racer takes his car from 42 m/s to rest by deploying the parachute. If it took 5. 5 seconds for the car to come to rest, what was its deceleration rate?

Standard Acceleration Graph Velocity (m/s) Time (sec) Remember because acceleration watches a trend/change of one object, we connect our data with a line.

Example 4: • Looking back at example 3, graph the deceleration of the drag car every half second from the time the brake is applied until the car comes to rest.

• Displacement during deceleration depends on acceleration, initial velocity and time. • displacement= ½(Vi + Vf) Δt

Example 5: • A race car driver reaches a max speed of 45 m/s, using a parachute (drag) and his brakes, the car comes to rest in 5. 5 seconds. Calculate the distance needed for braking.

• Displacement during acceleration depends on acceleration rate and time. • displacement=Vi Δt + ½ a(Δt )2

Example 6: • How long must a runway be (minimum) for a plane with the following conditions to take off safely? • a=4. 8 m/s 2 • t=15 sec • Vi = rest