Preliminary Questions 2B.1.1: Position, Velocity, Acceleration Plots

The plot to the right represents the motion of an object.

• During period 1, the object’s velocity is increasing, constant, or decreasing?

• Determine the velocity of the object at 20.0 s.

• During period 1, the object’s acceleration is positive, zero, or negative? Increasing, constant, or decreasing?

• Determine the acceleration of the object between 0.0 s and 15.0 s.

• Determine the distance traveled by the object during the first 10.0 s.

Prelim Q KEY 2B.1.1: Position, Velocity, Acceleration Plots

1. During period 1, the object’s velocity is increasing, constant, or decreasing?

First, note that the plot is of velocity [vertical] vs. time [horizontal]

Velocity starts the period at 0 m/s and increases uniformly to 15.0 m/s.

2. Determine the velocity of the object at 20.0 s.

15.0 m/s.

- Go to 20.0 s on the horizontal axis.- Move straight up [vertically] until you reach the plot [green, point B].- Move straight left [horizontally] until you reach the vertical axis [velocity].- Read the value.

Prelim Q KEY 2B.1.1: Position, Velocity, Acceleration Plots

3. During period 1, the object’s acceleration

is positive, zero, or negative?

Increasing, constant, or decreasing?

Acceleration = slope of v vs. t plot.

Slope between 0.0 s and 15.0 s is positive and does not change.

4. Determine the acceleration of the object between 0.0 s and 15.0 s.

ss

m

ss

m

sss

ms

m

tt

vv

t

va

initialfinal

initialfinal

00.10.15

0.15

0.00.15

0.00.15

Prelim Q KEY 2B.1.1: Position, Velocity, Acceleration Plots

5. Determine the distance traveled by the object during the first 10.0 s.

Distance from a v vs. t plot:Area under the curve.

Area of a triangle = ½ (base) (height)= ½ (10.0s) (10.0 m/s) = 50 m

OR:Distance = (avg. velocity) (time interval)

mssmss

m

sssm

sm

tvd avg

501050.102

0.10

0.00.102

0.100.0

Follow up questions. 2B.1.1: Position, Velocity, Acceleration Plots

The plot to the right represents the motion of an object.

• During period 2, the object’s velocity is positive, zero, or negative? Increasing, constant, or decreasing?

• During period 2, the object’s acceleration is positive, zero, or negative? Increasing, constant, or decreasing?

• Determine the acceleration of the object during period 2.

• Determine the distance traveled by the object during period 2.

• Determine the velocity of the object at 10.0 s.

KEY. Follow up. 2B.1.1: Position, Velocity, Acceleration Plots

The plot to the right represents the motion of an object.

• During period 2, the object’s velocity is positive, zero, or negative? Increasing, constant, or decreasing?

• During period 2, the object’s acceleration is positive, zero, or negative? Increasing, constant, or decreasing?

• Determine the acceleration of the object during period 2. Slope = zero.

• Determine the distance traveled by the object during period 2. (15 m/s)(5 s)=75 m

• Determine the velocity of the object at 10.0 s. 10.0 m/s.

Follow up questions, 2. 2B.1.1: Position, Velocity, Acceleration Plots

The plot to the right represents the motion of an object.

• During period 3, the object’s velocity is positive, zero, or negative? Increasing, constant, or decreasing?

• Determine the velocity of the object at 25.0 s.

• During period 3, the object’s acceleration is positive, zero, or negative? Increasing, constant, or decreasing?

• Determine the acceleration of the object during period 3.

• Determine the distance traveled by the object during period 3.

KEY. Follow up 2. 2B.1.1: Position, Velocity, Acceleration Plots

The plot to the right represents the motion of an object.

• During period 3, the object’s velocity is positive, zero, or negative? Increasing, constant, or decreasing?

• Determine the velocity of the object at 25.0 s. 5.0 m/s.

• During period 3, the object’s acceleration is positive, zero, or negative? Increasing, constant, or decreasing? Slope of a line is constant. Slope is negative.

• Determine the acceleration of the object during period 3. (15m/s – 5m/s)/(25s – 20s)=10/5=2m/s/s

• Determine the distance traveled by the object during period 3. ((15m/s + 5m/s) / 2) (25s – 20s) = 50m