PHYS 2211 Module 3 Self Assessment Practice Problems
Module 3 Self Assessment Practice Problems
A particle moves along the x-axis according to x(t) = 10t – 2t2 m.
(a) What is the instantaneous velocity at t = 2 s and t = 3 s?
(b) What is the instantaneous speed at these times?
(c) What is the average velocity between t = 2 s and t = 3 s?
Answer: (a) 2 m/s, -2 m/s (b) 2 m/s, 2 m/s (c) 0 m/s(Click and drag over the answer to highlight it)
Dr. John Paul Stapp was a U.S. Air Force officer who studied the effects of extreme acceleration on the human body. On December 10, 1954, Stapp rode a rocket sled, accelerating from rest to a top speed of 282 m/s (1015 km/h) in 5.00 s and was brought jarringly back to rest in only 1.40 s. Calculate his
(a) acceleration in his direction of motion and
(b) acceleration opposite to his direction of motion.
Express each in multiples of g (9.80 m/s2) by taking its ratio to the acceleration of gravity.
Answer: (a) 5.76g (b) 20.6g
A commuter backs her car out of her garage with an acceleration of 1.40 m/s2.
(a) How long does it take her to reach a speed of 2.00 m/s?
(b) If she then brakes to a stop in 0.800 s, what is her acceleration?
Answer: (a) 1.43 s (b) -2.50 m/s2
(a) Sketch a graph of velocity versus time corresponding to the graph of displacement versus time given in the figure.
(b) Identify the time or times (ta, tb, tc, etc.) at which the instantaneous velocity has the greatest positive value.
(c) At which times is the instantaneous velocity zero?
(d) At which times is the instantaneous velocity negative?
Answer: (b) td (c) tc, te, tg, tl (d) ta, tb, tf
(a) Sketch a graph of acceleration versus time corresponding to the graph of velocity versus time given in the figure.
(b) Identify the time or times (ta, tb, tc, etc.) at which the acceleration has the greatest positive value.
(c) At which times is the acceleration zero?
(d) At which times is the acceleration negative?
Answer: (b) ta (c) te, th (d) ti, tj, tk, tl
At t = 10 s, a particle is moving from left to right with a speed of 5.0 m/s. At t = 20 s, the particle is moving right to left with a speed of 8.0 m/s. Assuming the particle’s acceleration is constant, determine
(a) its acceleration,
(b) its initial velocity, and
(c) the instant when its velocity is zero.
Answer : (a) -1.3 m/s2 (b) 18 m/s (c) 13.8 s
A fireworks shell is accelerated from rest to a velocity of 65.0 m/s over a distance of 0.250 m.
(a) Calculate the acceleration.
(b) How long did the acceleration last?
Answer: (a) 8450 m/s2 (b) 0.0077 s
A care package is dropped out of a cargo plane and lands in the forest. If we assume the care package speed on impact is 54 m/s (123 mph), then what is its acceleration? Assume the trees and snow stops it over a distance of 3.0 m.
Answer: -486 m/s2
A kangaroo can jump over an object 2.50 m high.
(a) Considering just its vertical motion, calculate its vertical speed when it leaves the ground.
(b) How long a time is it in the air?
Answer: (a) 7.0 m/s (b) 1.44 s
A diver bounces straight up from a diving board, avoiding the diving board on the way down, and falls feet first into a pool. She starts with a velocity of 4.00 m/s and her takeoff point is 1.80 m above the pool.
(a) What is her highest point above the board?
(b) How long a time are her feet in the air?
(c) What is her velocity when her feet hit the water?