# Speed vs.Velocity Speed (s) is the distance an object travels per unit of time (rate). Speed (s) is the distance an object travels per unit of time (rate).

## Presentation on theme: "Speed vs.Velocity Speed (s) is the distance an object travels per unit of time (rate). Speed (s) is the distance an object travels per unit of time (rate)."— Presentation transcript:

Speed vs.Velocity Speed (s) is the distance an object travels per unit of time (rate). Speed (s) is the distance an object travels per unit of time (rate). Velocity (v) describes the speed and direction of a moving object. Velocity (v) describes the speed and direction of a moving object.

Velocity Objects undergoing motion will either have a constant or changing velocity Objects undergoing motion will either have a constant or changing velocity constant velocity = not speeding up or slowing down. constant velocity = not speeding up or slowing down. changing velocity = speeding up or slowing down. changing velocity = speeding up or slowing down.

Constant / Zero Velocity Distance (m) Time (s) Constant velocity Zero Velocity

Changing Velocity Distance (m) Time (s) Speed up Slow Down

Average Velocity When working with a constant velocity, we use the following equation. When working with a constant velocity, we use the following equation. ν avg =Δx / Δt Velocity Displacement Time Δ = change

Sample Problem What is the velocity of a runner that can travel 10 m in 5 seconds? What is the velocity of a runner that can travel 10 m in 5 seconds? ν avg =Δx / Δt ν avg = 10 m/5 s ν avg = 2 m/s

Acceleration changes velocity Acceleration (a): the rate of change of velocity. Acceleration (a): the rate of change of velocity. Objects can accelerate in both the + and - direction. Objects can accelerate in both the + and - direction. Velocity Time

Accelerating Car 0 100 Constant acceleration velocity Time

Car on cruise control 0 100 Zero Acceleration velocity Time

Negative Accelerating Car 0 100 - acceleration velocity Time

Acceleration (cont.) a avg = Δ ν /Δt = v f – v i Δt Δt acceleration SI unit = m/s² Final VelocityInitial Velocity

Sample Problem A car traveling at 7.0 m/s accelerates uniformly to a velocity of 12.0 m/s in 2.0 s. What is the acceleration of the car? V i = 7 m/s V f = 12 m/s a = v f – v i Δ t Δ t t = 2.0 s = (12.0 m/s – 7.0 m/s) = 2.0 s 2.0 s 2.5 m/s²

Changing Acceleration Velocity (v) Time ( Δ t) Forward Motion Reverse Motion Zero Motion

1-Dimentional Motion Equations V avg =Δx/Δt Δx = ½ (v i + v f ) Δt a = (v f - v i ) / Δt Δx = v i Δt + ½ aΔt² v f ² = v i ² + 2aΔx

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