Physics 101.003                        Test 3   Answers                April 20, 2004

 

Read each question and its set of answers very carefully.  There is only one best answer for each question.  Don’t be afraid to ask questions of me during the exam.  Just raise your hand if you have one.

 

  1.   Who classified motion into violent and natural?

(a) Aristotle                     (b) Galileo

(c) Newton                      (d) Copernicus

 

  2.   The tendency of objects to resist changes in motion is called

(a) friction                       (b) velocity

(c) inertia                        (d) acceleration

(e) gravity

 

  3.   What is the average speed of a horse that gallops a round‑trip distance of 15 km in a time of 30 min?

(a) 0                                 (b) 0.5 km/hr

(c) 30 km/hr                    (d) 500 m/s

(e) None of the above

 

  4.   The speedometer of your car gives you the instantaneous velocity of your car.

(a) True                           (b) False

 

  5.   A car goes from v = 0 to v = 50 m/s in 10 s.  If you wish to find the distance traveled using the equation d = (1/2)at2, what value should you use for a?

(a) 9.8 m/s2                      (b) 32 ft/s2

(c) 50 m/s                        (d) 5 m/s2

 

  6.   Which of the following are proper units for acceleration?

(a) kg/m2                                      (b) kg m/s2

(c) lb/ft2                                        (d) ft/s2

(e) ft2/s

 

  7.   A bullet is fired straight down from the top of a high cliff.  Neglecting air resistance, the acceleration of the bullet is

(a) less than 32 ft/s2                        (b) 32 ft/s2

(c) more than 32 ft/s2

 

  8.   An object in free fall falls 16 ft in the first second of fall.  How far does it fall in the second second of fall?

(a) 16 ft   (b) 32 ft           (c) 48 ft

(d) 64 ft   (e) 96 ft

 

  9.   What is the instantaneous speed of a rock in free fall after 5 seconds of a fall from rest?

(a) 160 m/s                      (b) 64 ft/s

(c) 96 ft/s                        (d) 32 m/s

(e) none of the above

 

10.   Which of Newton’s laws was being demonstrated in class when I threw the Nerf rock at some students on the second row?

(a) first                            (b) second

(c) third  


11.   Newton's concept of motion said that the natural state of an object was

(a) constant velocity       (b) constant acceleration

(c) constant net force

 

12.   Which is most directly associated with inertia? 

(a) force                          (b) velocity                      (c) mass

(d) acceleration               (e) gravity

 

13.   On the moon it is just as hard to start an object moving horizontally as it is to start it moving horizontally on the earth if there is no air resistance to contend with. 

(a) True                           (b) False

 

14.   Suppose you have two identical sealed cans, one filled with lead and the other empty, and you are in an orbiting space ship where the two cans are "weightless."  How could you tell which has the greater mass? 

(a) put them on a balance

(b) throw each of them at the guy who made up this question, if he is aboard

(c) measure their volumes

(d) do a free-fall experiment

(e) none of the above

 

15.   The unit of mass in the English system of units is the

(a) Newton                      (b) pound                        (c) slug                 (d) kilogram

 

16.   A person who weighs 160 lb has a mass of

(a) 160 kg                        (b) 5 kg

(c) 5 slugs                        (d) 10 slugs

 

17.   Which of the following is a scalar? 

(a) velocity                      (b) force

(c) acceleration               (d) all of the above

(e) none of the above

 

18.   An object has a 10 lb force applied to the left and a 5 lb force to the right.  What is the mass of the object if it undergoes a horizontal acceleration of 2 ft/s2 due to these two forces? 

(a) 7.5 slugs                     (b) 2.5 slugs

(c) 7.5 kg                         (d) 5 slugs

(e) none of the above

 

19.   What kind of motion does a constant net force produce on a body of constant mass? 

(a) uniform motion          (b) constant speed

(c) constant velocity       (d) constant acceleration

(e) none of the above

 

20.   The acceleration of a body is directly proportional to

(a) its speed                                                             (b) its velocity

(c) its mass                                                              (d) the force of gravity

(e) the net force applied to it

21.   Newton's second law says .  What is ?  

(a) the weight of the object m

(b) the friction acting on the object m

(c) the total (resultant) force acting on the object m

(d) the reaction force acting on the object m

 

22.   Does acceleration take place if a force is applied perpendicular to the direction of motion of an object? 

(a) Yes                            (b) No

 

23.   Your weight is 160 lb.  You are standing on bathroom scales inside an elevator that is accelerating downward.  What is the reading on the scales? (This is not free fall.)

(a) 160 lb

(b) less than 160 lb but greater than zero

(c) greater than 160 lb

(d) zero

 

24.   In a tug-of-war there exists 1000 N of pull on each side of the rope.  The net force exerted on the rope is

(a) 0 N                             (b) 500 N                         (c) 1000 N                  (d) 2000 N

 

25.   The force of friction is called           when there is no relative motion between contacting media?

(a) static                          (b) dynamic                     (c) kinetic                  (d) systematic

 

26.   When a falling body ceases to accelerate it is said to have reached its

(a) terminal velocity                                                (b) escape velocity

(c) terminal acceleration                                         (d) outer limits

(e) maximum height

 

27.   A 10 lb rock and a 10 lb bag of feathers are released at the same time to fall 100 ft through the air.  Which reaches the ground first?  (Do not ignore air resistance.)

(a) rock                           (b) feathers

(c) both reach at the same time

 

28.   What is the magnitude of the acceleration in m/s2 of a 5 kg object when the net force on the object is 9.8 N?

(a) 2.2                                  (b) 3.92                           (c) 1.96                               (d) 9.8

 

29.   A 10 lb weight is in free fall.  What does Newton's third law imply about this situation? 

(a) the net force on the weight is 10 lb

(b) the motion will be inertial

(c) the weight exerts a force of 10 lb on the earth

 

30.   A bug and a car collide.  Which experiences the greater force?

(a) bug

(b) car

Good Luck!!
 
(c) neither, they both experience the same magnitude of force

 

31.   You can’t touch without being touched.  Which one of Newton’s laws is being described?

(a) first                            (b) second                       (c) third

 

32.   An archer shoots an arrow.  Consider the action force to be the bowstring against the arrow.  Then the reaction force is the

(a) grip of the archer's hand on the bow

(b) arrow against the bowstring

(c) air resistance against the arrow

(d) friction of the ground on the archer's feet

(e) weight of the arrow

 

33.   The product of mass times velocity is most appropriately called 

(a) impulse                      (b) change in momentum

(c) momentum                 (d) change in impulse

 

34.   A force times time is most appropriately called

(a) a torque                                                             (b) an impulse

(c) an angular momentum                                       (d) a jerk

(e) a change in momentum

 

35.   What impulse in Nis is needed to stop a 1200-kg car traveling at 20 m/s?

(a) 20                               (b) 1200

(c) 60                               (d) 24,000

 

36.   In regards to impulse which of the following situations would you want to keep the time of contact large?

(a) hitting a baseball                                                (b) catching a baseball

(c) rolling with a punch                                           (d) all of the above

(e) none of the above

 

37.   Why does a person who jumps from an elevated position bend his knees when he hits the floor?  Because

(a) he is increasing the force acting on his body

(b) he is destroying energy

(c) the force of impact causes his body to bend his knees

(d) he is extending the time during which his momentum is changing

 

38.   A 1‑kg steel ball traveling at a speed of 10 m/s hits a wall and bounces off at a speed of 8 m/s.  A 1‑kg clay ball traveling at a speed of 10 m/s hits the same wall and sticks to it.  Which ball delivers the most punch (impulse) to the wall? 

(a) steel ball

(b) clay ball

(c) the same for both since they hit with the same velocity

 

39.   You are standing on a frictionless surface of ice.  You throw a 2‑kg object horizontally with a velocity of 20 m/s.  Your mass is 100 kg.  What is your horizontal speed in m/s?

(a) 20                               (b) 40

(c) 100                             (d) 0.20

(e) 0.40

 

40.   A Mack truck and a Volkswagen have a head‑on collision.  Which driver experiences the greater force?

(a) Mack truck driver

(b) Volkswagen driver

(c) both experience the same force