# Week 3 (Aug. 26 - 30)

**Reading:**PSE Chap 2, Motion in 1 dimension

**Topics:**This week, we begin our discussion of displacement, velocity, acceleration, free fall, and one- dimensional kinematics.

**No Quiz**this week.

**Week 3 HW problems:**

**Thrown object:**An object is thrown straight up wards from the ground level with a speed of 50 m/s. What is its distance from the ground 6 seconds later? Solution.**Dropped ball:**A ball is dropped from a 100 meter cliff. Assume that the acceleration due to gravity is 10 m/s^2.- What is the time it takes to strike the ground?
- What is its speed when it strikes the ground?
- Make a graph of the ball's (i) velocity versus time, (ii) acceleration versus time and (iii) height versus time.
- If the ball is perfectly elastic, so that its motion is reversed when it hits the ground, then how long will it take to get back up to 100 meters? What will be its speed at the top of its flight? What will be its acceleration at the top of its flight? Solutions.

**Accelerating object:**An object starts from rest at the origin and moves along the x-axis with a constant acceleration of 4 m/s^2. What is its average velocity as it goes from x=2 to x=8 meters? Plot the position, velocity, and acceleration versus time for this object. Solution.

**Classroom problems:**As a reminder, these are some of the problems we worked out in class…

- Uniform motion: how far does a car moving at 30 mph travel in 1, 2, 3 hours?
- Uniform acceleration: how far does a uniformly accelerating car travel if it speeds up from 0 to 30 mph in one hour?