# Week 3

Reading: PSE Chap 2, Motion in 1 dimension
Topics: displacement, velocity, acceleration, free fall, 1 dimensional kinematics

Lab: Ramp experiment next week

Homework Problems: Due Tuesday, Sept. 6,

1. 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.
2. 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?
3. 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.
4. A car, initially at rest travels 20 meters in 4 seconds along a straight line with constant acceleration. What is its acceleration? Make a plot of the position, velocity and acceleration of this car. Solutions.
5. How far does a car travel in 6 seconds if its initial velocity is 2 m/s and its acceleration is 2 m/s^2 in the forward direction? Solution.
6. A particle's position is given by x(t) = 12 t - 3.0 t^2. What is v(t)? What is a(t)? Make a sketch of its position, velocity and acceleration versus time. Is the particle ever at rest? If so, when? Solution.

Quiz: yes. Covering weeks 1 and 2.
AP Physics