# Reading Assignment: (3.1)

## Presentation on theme: "Reading Assignment: (3.1)"— Presentation transcript:

What is this vector indicating? A velocity with a 1.5 cm component A displacement with a 1.5 cm component A displacement vector with the components (3.0 cm, 4.5 cm) A position vector to a place at (3.0 cm. 4.5 cm)

Short exercise Draw the picture for the following problem, label, and write an appropriate vector equation: In a dance, you are standing in a spot, and your partner is located 5 steps to the right of you. He takes 5 steps back, 10 steps to his left. Which displacement does he need to undergo to end up beside you?

Short exercise Draw the picture for the following problem, label, and write an appropriate vector equation: You are observing deer. First, you spot the buck 200m at NNE. A few seconds later, he surfaces again north of you. From the time that has passed you determine that the buck can not have further than 80 m away from the first position. What is the buck’s new position vector?

Refinement for average velocity
Displacement vector Position vector Time t2 Position vector Time t1 observer defines reference point Average velocity: change in position over time Position vectors: bound to a reference point

You watch a ground hog poke his head out of a hole 20m due North of your position. About 15 s later, he appears at a distance of 45 m West of you. Determine its displacement. Determine its average velocity.

Instantaneous velocity
Direction of average velocity? Strategy: bring the two points closer together.

Instantaneous velocity

Instantaneous velocity

Velocity vector? Speed? What are those components?

Average acceleration Change in velocity? Rate of change in velocity?
Average acceleration is the average rate of change in instantaneous velocity.

Instantaneous acceleration
Change in velocity?

Which of the particles below has zero acceleration? A baseball is flying beyond the playing field for a home run. A child in a Ferris Wheel being spun around at constant speed. A glider is sliding off an inclined air track. A car is slowing down on an icy straight road.

A ship’s echo on a radar screen is
moving according to in which all lengths are in km and times in hours. Find the position at time zero, after 30 min and after 1 hour. Find the velocity as a function of time; then calculate it at time zero, 30 min and 1h. Find the acceleration as a function of time; then calculate the acceleration at zero. 30 min and 1 h. Draw positions into an x-y coordinate system, and indicate the respective velocity and acceleration vectors.

Example A toy train is traveling around a circular track. Its position changes with time as Find the position of the train after 5 s. Find the velocity of the train after 5 s. y x