Bell Ringer
1.
If the velocity of a particle is nonzero, can
the particle’s acceleration be zero? Explain
2.
If the velocity of a particle is zero, can the
particle’s acceleration be zero? Explain
3.
If a car is traveling eastward, can its
acceleration be westward? Explain
4.
If the average velocity of an object is zero in
some time interval, what can you say about the
displacement of the object during that interval?
Practice Problem 1
A car is traveling due east at 25.0 m/s at some
instant.
a) If its constant acceleration is 0.750 m/s^2
due east, find its velocity after 8.50 s have
elapsed.
b) If its constant acceleration is 0.750 m/s^2
due west, find its velocity after 8.50 s have
elapsed.
Practice Problem 2
A car traveling east at 40.0 m/s passes a trooper
hiding at the roadside. The driver uniformly
reduces his speed to 25.0 m/s in 3.50 s.
a) What is the magnitude and direction of the
car’s acceleration as it slows down?
b) How far does the car travel in the 3.5 s
period?
Practice problem 3
(Involving 2 objects)
A car traveling at a constant speed at 24.0 m/s
passes a trooper hidden behind a billboard
One second after the speeding car passes the billboard,
the tropper sets off in chase with a constant
acceleration of 3.00 m/s^2.
a) How long does it take the trooper to overtake the
speeding car?
b) How fast is the trooper going at that time?
Practice Problem 4
(Involving two objects)
A motorist with an expired license tag is
traveling at 10.0 m/s down a street
And a policeman, taking another 5.00
s to finish his donut, gives chase at an
acceleration of 2.00 m/s^2.
Find
a) The time required to catch the car
b) The distance the trooper travels while
overtaking the motorist
Practice Problem 5 (Involving
horizontal motion with two phases)
A typical jetliner lands at a speed of 160 mi/h
and decelerates at the rate of (10 mi/h)/s.
If the plane travels at a constant speed of 160 mi/h for
1.0 s after landing before applying the brakes…
…What is the total displacement of the aircraft between
touchdown on the runway and coming to rest?
Practice Problem 5 (Involving
horizontal motion with two phases)
A jet lands at 80.0 m/s, the pilot applying the
brakes 2.00 s after landing. Find the
acceleration needed to stop the jet within
5.00 x 10^2 m.