# 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. We will start with the concepts of

*constant velocity, constant acceleration, and the mean speed theorem*.

**Homework Problems:**Due Thursday of week 4 (two days after you get back from Labor day)

- Ramp laboratory experiment (Ramp lab is due Monday of Week 5)
- Set up a ramp. Measure the angle of the ramp with respect to the horizontal desktop.
- Roll a small steel ball down the ramp. Record the time the ball takes to roll 10, 20, 30, 40,
*etc.*cm down the ramp. Be sure to record experimental uncertainty. - Repeat this procedure for three different ramp angles.
- Make a plot of the distance (ordinate) as a function of time (abscissa) using graphical analysis software. Label your plot appropriately.
- Put the data from all three data sets on the same graph; for each data set perform a power-law fit to the data. Does your fit match your expectations?
- Using the kinematic equations we've learned this week, determine the acceleration of the ball from your graphs.
- 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.
- A ball is dropped from a 100 meter cliff. Assume that the acceleration due to gravity is 10 m/s^2. Solution.
- 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?

**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?