APB – Multiple Choice Practice QuestionsDynamics – no circular motion

25) A26) E38) A

6) C34) A38) D

o. The reaction force doe' not caillcd the' action) forc,e becau 'e:TIle action for,ce i greater than the reac ion force.The action force is less than the reaction force.

, They act on difFerent bodies.TIl'eyare in tile arne direction.Thee reaction exi 'ts only after the action force i, relDoved.

34. A ,tudent pulls a wooden box along a rough horizontalfloor at con tant speed by means of a force P as shown to theright. Which of the following must be true? fA. P > f and < \V. ~-----i

B. P > fand . = "v.c. P = fand N > '"V. \".1D. P = f and N = Vol.

E. P<fandN=W.

38. A block Vi, ith initia velocity 4.0 mfs slides 8.0 macros a rough horizontal floor beforecoming to rest. The. coefficient of fric.tion is:

A. 0.80 B. 0.40 D. 0.10 E. 0.05

15) C30) C32) A33) D39) B

15. A car who e mass i 1500 kg is accelerated uniformly ii-om re 't to a speed of20 m/s in 10 s.The magnitude of the net force accelerating the car i :A. 1000 B. 2000 C.. JOOO D. 20000 N E. 30000 N

30. An 800-kgelevator accelerates downward at 2.0 m/s2 . The force exerted by the cable on theelevator is:

A. 1.6 kN down B. 1.6 k up C. 6.4 kN up D. 8.0 kN down E. 9.6 k down

32. The 10.0 kg box shown in the figure to the right isliding to the right along the floor. A horizontal force of10.0 N is being applied to the right. The coefficient ofkinetic friction bet\¥een the box and the floor is 0.20. Thebox is moving "vith:

A. acceleration to the left.

B. centripet~l acceleration.

C. acceleration to the right.

D. constant speed and constant velocity.

E. constant speed but not constant velocity.

v

I I10.0 N

__ 10.0 I<g __

y

33. Two blocks X and Yare in contact all ahorizontal frictionless urface. A 36 Neon tantforce is applied to X as shown to the right. Theforce exerted by X on Yis:

A. 1.5 N B. 6.0 C. 29 D.30N E.36N

39. A sume the objects in the following diagrams ha\e equal ma s and the strings holding them inplace are identical In which case would the tring be most likely to break?

A. B. c. E. All wouldbe equally likelyto break.

30) C31) E

30. A Stllllg with masses of 1.5 kg and 3.0 kg on its ends is IllUlg o\"er africtionless. massless pulley as showll. to the right. Whar is the approximatemagnitude of me acceleration of the masses?

A. 1.5 In/52B. 3.0 tn/52

C. 3.3 tn/52D. 6.7111/52

E. 10 Ill/52

•

I 15."!j

3.0 kg

31. Two blocks of mass 1.0 kg and 3.0 kg are cOIUlectedby a string which has a tension of 2.0 N. A force Factsill the direction shown to the right. Assuming fnction isnegligibIe. whm is the value ofF?

---llkg~ 3kg ~

A. 1.0 N B. 2.0 N C. 4.0N D.6.0N E. S.ON

3) D25) E29) B31) E

3. An obje.ct in equilibrium has three force FI of 30 N, Fz of 50 Nand F3 of 70 , acting on it.The magnitude of the re ultant ofFI and Fz is

A. 10 B. 20N C. 40 I D. 70 E.80N

25. A car whose mas is 1200 kg is accelerated fi'om rest by a constant force of 2400 N. \Vhat isthe speed of the car 8.0 s after beginning?

A. 0040 mls B. 1.. 6 mls C, 4.0 mls D. 8.0 mls E. 16 mls

29. A 50-kg student stands on a scale in an elevator. At the in tant the elevator has a downwardacceleration of 1,0 mlsz and an upward velocity of 3,0 mis, the ca.1e read approxim.ately

A.350 I B, 450 C. 500 D. 550 N E. 650 N

31. An object sliding dov..'n all inclined plane has speed 0.40 mls two seconds after it begins toslide. Approximately how far does it travel in three seconds?

A. 0.1- m B. 0.30 ill C, 0.45 m D. 0.60 ill E. 0.90 ill

3. If the net force on an object \vere doubled while at the same time the rna s of the object wa 'halved then the acceleration of the object is

[A] 1/4 as great..[B] ] /2 as great.[C] 2 times greater.[D] 4 times greater.[E] unchanged.

5. A tractor-trailer 11uck is traveling down the road. The mass ofthe trailer i 4 time the rna' of the tractor. If the tractoraccelerates fmward, the force that the trailer applies on the tractor1S

[A] 4 times greater than the force of the tractor on the trailer.[B] 2 times greater than the force ofthe tractor on the trailer.[C] equal to the force of the tractor on the trailer.[D] 1/4 the force of the trac.tor on the trailer.[E] zero ince the 11"actor is pulling the trailer forward.

-""l I Trailer ~~L--------,od

8. A weight can be hung in any of the following four way . In which case is the string most likelyto break.

[A] A

A

w

[B] B

B c

[C] C [D] D [E] all the same

] 2. Two boxe are accelerated to the right on a.frictionles horizontal surface as shown. The larger boxhas a tIl.as of 9 kilograms and the smaller box has a rna sof .; kilogralns. If a 24 newton horizontal force pulls onthe la.rger box with what force does the larger box pull onthe malleI' box.

24 N9 kg

[A] 3 N [B] 6 [C] 8 [D] 18 N [E] 24

3) D 5) C 8) B 12) B 16) E 32) C 33) B 36) E

16. \'\'hich of the following principle best explain why large tractor-trailer bucks generallyaccelerate much more lowly that automobiles?

[A] To e\ elY action there is an equal reaction.[B] E,eIY body attmcts evelY other body in the uni\ erse.[C] A force is nece salY to change the speed or direction of a body.[D] The total momentum of interacting bodies is always conserved.[E] The acceleration of a body i inversely proportional to its rna s and directly proportionalto the external force acting on the body.

FJ A

[A] the frictional forc·e i the same in both ca e'[B] the inclined case has a greater frictional force[C] the inclined case ha,s les frictional force[D] tIle frictional force increase with angle until the angle is 90° then drops to zero[E] more infOlmation is required

3~. A wooden box is first pulled aero s a horizontal steel plate asshown in the diagram A. The box is then pulled acro s the samesteel plate while the plate is inclined as shown in diagram B. Hov.does the force required to overcome friction in the inclined case(B compare to the horizontal case (A)?

33. One object at the surfac·e of tile Moon experience' the ame gravitational force a a secondobject at the surface of the Earth. \Vhich of the following would be a reasonable conclusion?

[A] both objects would fall at the same acceleration[B] t1le object on the Moon has the greater mass[C] the object on the Earth ha the greater mass[D] both object have identical masse[E] the object on Earth ha a greater ma but the Earth has a greater rate of rotat.ion.

36. \Vhat happens to the inertia of an object. when it 'e1ocity is doubled?

[A] the object s inertia becomes .J2 times greater[B] the object's inertia become 2 times greater[C] the object's inertia becomes 4 times greater[D] the object inertia become 8 times greater[E] the object's ineliia is unchanged

13) B25) C26) B32) C

1..;.J

An object near the surface of the earth with a weight of 100 newtons i accelerated at 4 m/·-.\\That is the net force on the object?

A) 25 N B) 40N C) 250 D) 400 N E) 2500 N

25. The net force on a rocket with a weight of 1.5 x 104 newtons is 2.4 x 104 newtons. About howmuch time is needed to increa e the rocket's speed fi:om 12 m/s to 36 lIlts near the smface of theEarth at takeoff?

A) .62 seconds B) .78 seconds C) 1.5 seconds D) 3.8 second E) 15 seconds

26. A SaO-gram ball moving at 15 mls slows down uniformly until it stops. If the ball tra, els 15meters, what was the average net force applied while it was coming to a stop?

A) 0.37 newton B) 3.75 neVi tons C) 37.5 newtons D) 375 newtons E) 3750 new10ns

32. A block rests on a flat plane inclined at an angle of 300 with reo pect to the horizontal. 'What ithe minimum coefficient of fi'iction nece sary to keep the block from tiding?

A)~

2

B) 1

.fiC) 1

J3D) 1

4

E) 2

13

7) C11) C12) B

7. A force of 6 newtons and a force of 10 newton can be combine to form a re ultant with amagnitude of\\hich of the following

A) 0 newton B) 2 newton C) 8 newtons D) 20 newtons E) 60 newtons

QUE'stions 11 and 12 l'E'f('1' to the following sc('nal'io:A 5 kg block re ts 011 a flat plane inclined at an angle of 30° to the horizon as hown in the diagrambelow.

2E) 10 mls2D) 8.7 mlsC) 5 m/s22B) 0.87 mls

11. What would be the acceleration of the block down the plane assuming the force of friction inegligible?

A) 0.5 mfs2

12. lfthe block is placed on a second plane (where fi:iction i ignificant) inclined at the same angle,it '" ill begin to accelerate at 2.0 m/s. What is the force of friction between the block and the secondinclined plane?

A) 10 N B) 15 N C) 25 D) 43.3 N E) 50 N

20) D 36) C 40) D

THE NEXT THREE QUESTIONS REFER TO THE FOLLO\VING SCENARIO

A 2 kg mas and a 4 kg mass on a horizontal frictionless surface are connected by a massless stringA. TIley are pulled horizontally across the surface by a econd string B with a constant accelerationof 12 mfs2

.

6. \Vhat is the magnitude of the force of tring B on the 2 kg rna's.A 72 B) 48 C) 24 D) 6 N E) 3N

7. \Vhat is the magnitude of the force of tring A on the 4 kg mass?A) 72 B) 48 C) 24 D) 6 N E) 3N

8. \Vh.at is the magnitude of the net force on the 2 kg mass?A) 72 B) 48 C) 24 D) 6 N E) 3 N

THE NEXT THREE QUESTIO S REFER TO THE FOLLO\VING SCE TARlO

,++,+,

~---4··· .+ .... + .... + .... + .... + .... + .... +

... + ... +. .. + .

.... + .... + .... + .... +. . ... + .... + .... + .... + .... +

2

. . . . . . . . . ., Time In,seconds '

.~ 0+<::-----+--,-,-2+-,---+------,14"-,---+----+6-,---+--,-,-+-B----+--1+-n

"~> -1

The accompanying graphdescribe the motion of atoy car across the floor for10 econds.

26. At v.hat times or time intervals must the net force on the toy car be zero?A) at t = 4 s onlyB) at t = 0 s, at t = 4 s and at t = 10 s onlyC) from t = 2 to t = 3 sand fi-om t = 6 s to t = 9 onlyD) from t = 0 s to t = 2 , fiom t = 3 s to t = 6 sand IT'om t = 9 s to t = 10 'onlyE) the entire time IT'om t = 0 s to t = 10 s

6) A 7) B 8) C 26) C 42) A

2) D40) D

6. The students in a Physic-s I c a \\ ere inlab conducting an experiment related toNe\¥ton's econd Law. The collecteddata were di played on the graph at theright. From this graph, what conclusioncan dIe tudent' make?

(a) The mass of the y tem wasconstant.

(b) The acceleration of the y temwa constant.

25

20

,-,15oQ

::; 10r

o

/

~/

/V

/'"

/"

//

1/V

(c) The force acting on the system 0wa constant.

(d) The force acting on the system is notrelated to the acceleration of the system.

(e) The force acting on any y tem will always be Ie

0.2 0.4 0.6 0.8

Acceleration nlls-)

than 20 I •

1.0

8. 'Why do raindrop faU with constant speed during the later 'tages of their de 'cent?

(a) The gravitational force is the ame for all drops.(b) All drop fall fi'om the same height.(c) The gravitational force i. negligible for object as small a' raindrops.(d) The gravitational force can110t increa e the speed of a falling object to more

than 9.8 m/ '.(e) Air resistance balance the gra\ itational force on a drop.

6) A8) E10) A14) E

10, A homeowner pushes a lawn mmver acro s a horizontalpatch of grass with a con 'taut speed by applying a forceP. The alTO\\{' in the diagram conectiy indicate thedirections but not necessarily the magnitu,des of the\ arious forces on the lav. n mower. \Vhich of thefoHowing relations aluong the various forc.e magnitude; •W, t N, P i CORRECT?

P>fandN>WP<fandN= WP>fandN< WP=fandN>Wnone of the above

14. An astronaut on the Moon in:mltaneOllsly drop a feather and a hanuner. The fact thatthey reach the surface at the same instant hows that

(a) no gravity forces ad on a body in a "\ acuum.(b) the acceleration due to gravity on the Moon is les. than the acceleration due to

gravity on the Eat1h.(c) the gravitational force fi'orn the Moon on heavier objects (the. hammer) is equal

to the gra 'itational forc·e on lighter ob' eels (the feather).(d) a hammer and feather have less mass on the Moon than on Earth.(e) in the ab ence of air resistance all bodies at a given location fall with the 'arne

acceleration.