PHY 113, Summer 2007
Langenbrunner
HW 3 – due Thursday, May 31 (by 5:00 PM)
1. The figure below shows that a particle moving along an x axis undergoes three periods of
acceleration. Without written computation, rank the acceleration periods according to the
increases they produce in the particle's velocity, greatest first.
(Hint: think about the relationships between the graphical representation of velocity and
acceleration.)
2. The position of a particle is given by x=(20m/s)t-(5m/s3)t3.
a) When, if ever, is the particle's velocity zero?
b) When is its acceleration zero?
3. The figure below shows four tracks (either half- or quarter-circles) that can be taken by a train,
which moves at a constant speed. Rank the tracks according to the magnitude of the train's
acceleration on the curved portion, greatest first.
4. The airport terminal in Geneva, Switzerland, has a "moving sidewalk" to speed passengers
through a long corridor. Larry does not use the moving sidewalk; he takes 150 s to walk through
the corridor. Curly, who simply stands on the moving sidewalk, covers the same distance in 70 s.
Moe boards the sidewalk and walks along it. Assuming that Larry and Moe walk at the same
speed, how long does it take Moe to move through the corridor?
5. A projectile is fired with initial speed vo=30.0m/s from level ground at a target that is on the
ground, at distance R=20.0 m, as shown below. Find the launch angles that will allow the
projectile to hit the target.