Physics 101 - Homework 5

Instructions: Complete this form and click submit. The answers will be posted on the course home page after the due date and before the next exam. If you want to change any of your answers after you click submit, then go back and give your answers again and click submit.

Your Name: e.g. John Doe
Your Campus ID: e.g. 12345678
Your SFA Email Address: e.g. doejd@titan.sfasu.edu
Due Date 11/6/2007 5:00PM

0. Some of the questions below have been modified from the in-class handout to test your understanding of the material. Try to answer these first without looking at the handout, then study the handout, modify your answers if necessary and click Submit.

I understand *
I do not understand

1. Which of the following is not proper units for acceleration?

(a) km/h.s
(b) m/s2
(c) m2/s *

2. The speedometer of a car indicates a constant speed. Can the car be accelerating?

(a) Yes *
(b) No

3. A body falls from rest. If air resistance is negligible, what is the velocity of the body after falling for 0.1 second?

(a) 10 m/s
(b) 9.8 m/s
(c) 98 m/s
(d) 0.98 m/s *
(e) 490 m/s

4. A rifle is fired straight downward from a high-altitude balloon. If the bullet leaves the barrel at 100 m/s, then its speed one second later (neglecting air resistance) will be about

(a) 9.8 m/s
(b) 98 m/s
(c) 104.9 m/s
(d) 109.8 m/s *
(e) 90.2 m/s

5. What is the speed of a rock at the top of its trajectory when thrown straight up?

(a) 0 m/s *
(b) 4.9m/s
(c) 9.8 m/s
(d) 490 m/s
(e) 9.8 m/s2

6. What is the acceleration of a rock at the top of its trajectory when thrown straight up?

(a) 0 m/s2
(b) 4.9m/s2
(c) 9.8 m/s2 *
(d) 4.9 m/s
(e) 9.8m/s

7. Which of the following balls would hit the ground first if they were all dropped at the same time from the same height (20 ft) in a vacuum?

(a) 15-lb feather ball
(b) 20-lb wood ball
(c) 10-lb lead ball
(d) they all hit at the same time *

8. The two measurements necessary for calculating speed are

(a) velocity and time
(b) distance and time *
(c) distance and acceleration
(d) velocity and distance

9. What is the acceleration of a vehicle that changes is velocity from 10m/s to a dead stop in 10 seconds?

(a) -1m/s2 *
(b) -100 m/s2
(c) -0.01 m/s2
(d) 0 m/s2
(e) +100 m/s2

10. You throw a ball straight up. On the way up…

(a) the velocity and acceleration both have an upward direction
(b) the velocity has an upward direction and the acceleration has a downward direction *
(c) the velocity and acceleration both have an downward direction
(d) the velocity has an downward direction and the acceleration has a upward direction

11. The net force on any object in equilibrium is

zero. *
9.8 meters per second squared.
equal to its weight.
None of these.

12. The hang time (time off the floor in an unassisted jump) of professional basketball players is typically

less than 1 second. *
1 second.
2 seconds.
more than 2 seconds.

13. If a 100-lb. person steps on a pair of bathroom scales and leans so that the reading on one scale is 60 lbs., the reading on the other scale is

also 60 lbs.
40 lbs. *
less than 40 lbs.

14. Swing a rock overhead in a horizontal circle, and if the string breaks the rock will follow a ______________.

straight-line path. *
spiral path.
wider circle.
same-size circular path.

15. If you have snow on your boots, you can get the snow off by stamping your boots on the floor. This is in accord with the law of

equilibrium.
tension.
inertia. *
action and reaction.

16. If you exert a horizontal 100-N force on a crate and it slides along a factory floor at constant speed, then the friction between the crate and the floor is

somewhat less than 100 N.
100 N. *
somewhat more than 100 N.
something that can't be known, but only guessed.

17. The thing that distinguishes speed from velocity is

magnitude.
time.
time squared.
direction. *

18. If a car increases its velocity from zero to 50 km/h in 5 seconds, its average acceleration is

5 km/h/s.
10 km/h/s. *
actually the same as the acceleration of free fall.
Two of these.
None of these.

19. Toss a ball upward at 10 m/s, and the time it takes to reach its highest point is about

1 second. *
2 seconds.
10 seconds.

20. Toss a ball upward at 30 m/s and if air drag is negligible, the ball will be in the air for

3 seconds.
6 seconds. *
10 seconds.
more than 10 seconds.

21. Drop a ball and it accelerates at 9.8 m/s2. If you instead throw it downward, then right after it leaves your hand, assuming no air drag, its acceleration is

more than 9.8 m/s2.
still 9.8 m/s2. *
actually less than 9.8 m/s2.
...cannot say, unless the speed of the throw is given.

Need more examples or assistance?  If you have a new text book then you may be able to access tutorials and online quizes at www.PhysicsPlace.com.  The Access Code for this site is normally included in the first few pages of the book. See Dr. B for help during these office hours.