Graph 2: A car travels at a constant speed of 6 m/s (S = 30 m/5 s). The graph of constant speed is a slanted straight line. Notice that the speed is the same at every point on the graph. How far does the car go in 4 seconds?

Variables: S = 6 m/s; t = 4 s; d = ?

Formula:

Solution:

Graph 3: The same car travels at a constant speed of 1.0 m/s (S = 10 m/10 s). The graph of constant speed is a slanted straight line. Notice that the slope of the line is more gradual and every point on the graph has the same speed. How far does the car go in 4 seconds at its new speed?

Variables: S = 1.0 m/s; t = 4 s; d = ?

Formula:

Solution:

A bike moves 50 m in 10 seconds.Calculate the speed of the bike.

A car travels 200 miles east in 4 hours.Calculate the car’s speed.

A car travels 60 m/s for 10 seconds, north.Calculate how far it traveled.

AccelerationExample: A plane starts at rest and ends up going 200 m/s in 10 seconds. Calculate the acceleration.

Step 1: Variables: Vi = starting speed = 0 m/s (“starts at rest”); Vf = ending speed = 200 m/s, ∆t =10s

Deceleration (Negative Acceleration)Example: A race car starts at 400 m/s and then stops in 20 seconds. Calculate the car’s acceleration.

Step 1: Variables: Vi =400 m/s; Vf = 0 m/s; ∆t = 20 m/s

*** Take note of the negative sign. This represents deceleration or slowing down.

PRACTICE PROBLEMS

1. A biker starts to move and goes from 0 m/s to 25 m/s in 10 s. What is the acceleration?

Variables:

2. A biker goes from a speed of 20 m/s to 8 m/s in 6 s. What is the acceleration?

Variables:

3. A driver starts his parked car and attains an acceleration of 3 m/s2 in 5 seconds. What is the final speed?

Variables: