Week 3 (Aug. 26, 27, 28)
Reading: PSE Chap 2, Motion in 1 dimension
Topics: Estimation, displacement, velocity, acceleration, free fall
No Quiz this week.
Week 3 exercises:
Classroom problems: As a reminder, these are some of the problems we worked out in class…
No Quiz this week.
Week 3 exercises:
- Orbital speed estimation: Estimate the speed of the earth as it orbits around the sun. Hint: the earth is bit under 100 million miles from the sun. Don't look up any other numbers in books or on the internet or anywhere. Remember: when estimating, round to just one significant figure. No calculators! If you have to use a calculator, you are doing it wrong.
- Spiders estimation: Estimate the number of spiders inside your house. Do not look up any numbers anywhere, and explain your reasoning. And again: no calculators!
- Ping pong balls estimation: Estimate the number of ping pong balls can be placed (in a single layer) on the surface of Lake Michigan? Do not look any numbers anywhere, and do not use a calculator! What quantities do you need to estimate? What assumptions must you make?
- 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 3 seconds later? Six seconds later? At what time does it strike the ground?
- Dropped ball: A ball is dropped from a 100 meter cliff. Assume that the acceleration due to gravity is 10 m/s^2. (a) What is the time it takes to strike the ground? (b) What is its speed when it strikes the ground? (c) Make a graph of the ball's (i) velocity versus time, (ii) acceleration versus time and (iii) height versus time. (d) If the ball is perfectly elastic, so that its motion is reversed the moment 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?