= 40 N. Q = 60 O m s,k

Transcription

1 Multiple Choice ( 6 Points Ech ): F pp = 40 N 20 kg Q = 60 O m s,k = 0 1. A 20 kg box is pulled long frictionless floor with n pplied force of 40 N. The pplied force mkes n ngle of 60 degrees with the horizontl. If the box strts from rest, wht is the ccelertion of the box nd how fst is it moving fter thirty seconds?. The ccelertion is 3 m/s 2 nd the velocity is 40 m/s. b. The ccelertion is 1 m/s 2 nd the velocity is 30 m/s. c. The ccelertion is 2 m/s 2 nd the velocity is 40 m/s. d. The ccelertion is 1 m/s 2 nd the velocity is 60 m/s. e. None of the bove. =m x F pp cos =m x 40 N cos60 o =20kg x 40 N cos60o x = =1m/ s 2 20kg v x =v o x x t=0 m/s 1m /s 2 30 s=30 m/ s 40 kg v O = 30 m/s m s,k = A box with mss of 40 kg moves long with speed of 30 m/s when it encounters rough section of the floor where there is 0.20 coefficient of friction. The box slows nd comes to stop. Wht is the distnce the box slides fter it encounters the friction until it comes to rest? m b m c m d. 0.0 m e. None of the bove. =m y mg=0 =mg =m x f =m x =m x m g=m x x = g= m/s 2 = 1.96m/ s 2 2 v 2 x =v 2 ox 2 x 0=v 2 ox 2 x x= v o x 2 = 30m/s m/s 2 =229.59m

2 3. An exmple of the ction-rection pir of forces described by Newton's third lw re:. the norml force nd the weight of book sitting on the tble. b. the frictionl force nd pplied force exerted on box drgged cross floor. c. the grvittionl force of mss A on mss B nd the grvittionl force of mss B on mss A. d. the frictionl force nd norml force on box drgged cross floor. e. None of the bove. 4. A 60 kg jumps out of n irplne with prchute. He decides not to pull the rip cord until he reches terminl velocity. If the drg force is equl to F D = bv nd b=2kg/ s, wht is the mgnitude of the velocity when he decides to pull the cord? m/s b m/s c m/s d. 9.8 m/s e. None of the bove. =m y bv mg=m y bv T mg=0 v T = mg b = 60kg 9.8m/ s2 =294m/ s 2kg /s m=60 kg h = 6m 60 O 5. A 60 kg box strts from rest nd slides down frictionless rmp with n incline of 60 degrees. Wht is the ccelertion of the box down the rmp? m/s 2 b m/s 2 c m/s 2 d m/s 2 e. None of the bove. =m x mg sin =m x x =g sin =9.8m/ s 2 sin 60 o =8.49m/ s 2

3 6. A 30 kg bll is dropped from rest from height of 40 meters. Wht is the mximum velocity reched by the bll before it hits the ground?. +28 m/s b. -28 m/s c. +20 m/s d. -20 m/s e. None of the bove. =m y mg=m y y = g= 9.8m/s 2 v 2 y =v 2 o y 2 g y v y = 2 g y y o = 2 9.8m /s 2 40 m 0m =28m/s v= 28m /s or PE i KE i =PE f KE f mgh i 0=0 1 2 m v 2 f v f = 2 g h i v f = 2 9.8m/ s 2 40m=28m /s v f = 28m /s 20 kg 10 kg w = g 7. A 20 kg block sits on frictionless tble. A string is ttched which hngs over frictionless pulley. A 10 kg block hngs over the end. Wht is the mgnitude of the ccelertion of the 20 kg mss?. 4.9 m/s 2 b. 9.8 m/s 2 c. 20 m/s 2 d. 15 m/s 2 e. None of the bove. = = g = = g = m g 2 = 10 kg 9.8 m/ s2 =3.27 m/ s2 20 kg 10 kg

4 r = 50 m m f m = 0.3 w = mg 8. A 1000 kg cr rounds 50 meter rdius curve t constnt speed. The coefficient of friction of the rod is 0.3. Wht is the force which lets the cr mintin its speed s it negotites the curve?. grvittionl force b. norml force c. frictionl force d. weight e. None of the bove. 9. A 1000 kg cr rounds 50 meter rdius curve t constnt speed. The coefficient of friction of the rod is 0.3. Wht is the mgnitude of mximum velocity which the cr cn sfely negotite the curve? m/s b m/s c. 9.8 m/s d m/s e. None of the bove. =m y mg=0 =mg =m x f =m x mg=m v2 r v= r g= m/s2 50=12.12m/ s

5 30 kg + 60 kg 10. Atwood's mchine consists of frictionless pulley nd two msses connected by cble over the pulley. Wht is the mgnitude of the ccelertion of the msses? m/s 2 b m/s 2 c m/s 2 d m/s 2 e. None of the bove. = g = g = g = g g = 60kg 30kg g= 60kg 30kg 9.8m/s2 =3.27m/s 2

6 Problem One ( 20 Points ): 20 kg 10 m 60 O m s,k = 0.1 Not drwn to scle. A m s,k = 0.3 B A 20 kg block strts from rest t the top of 60 degree incline nd slides down the incline. There is 0.1 coefficient of friction on the rmp. The block then continues to slide long the horizontl surfce where there is 0.3 coefficient of friction. The block then slows, due to friction, until it comes to rest t point B.. (2) Wht is the mgnitude of the force due to grvity (i.e. the weight ) of the block on the incline? b. (2) Wht is the mgnitude of the Norml Force on the block on the incline? c. (2) Wht is the mgnitude of the frictionl force on the block on the incline? d. (2) Wht is the mgnitude of the ccelertion of the block down the incline? e. (3) Wht is the velocity of the block t Point A? f. (3) Wht is the mgnitude of the force of friction on the block on the horizontl? g. (3) Wht is the ccelertion of the block long the horizontl? h. (3) Wht is the distnce between Point A nd Point B?.) w=mg=20 kg 9.8 m/ s 2 =196 N b.) =m y mg cos =0 =mg cos =196 N cos60 o =98 N c.) f = = N =9.8 N d.)mg sin f =m 196 N sin 60 o 9.8 N =20 kg =8.00 m/ s 2 e.)sin = h x f.) f = mg= kg 9.8m/ s 2 =58.8 N g.) x = 58.8 N 20kg h.) v 2 =v o 2 2 x x= v 2 v o 2 2 = 2.94m/s 2 = m/s 2 =31.41 m m/ s 2 x= h sin =10m sin 60 o =11.55 m v 2 v o 2 2 x v = 2 x= 2 8 m/s m=13.59 m/s

7 Problem Two ( 20 Points ): + Wht is the ccelertion nd direction of the ccelertion of the 40 kg mss? : = y g cos =0 = g cos = f mg sin = mg sin = g cos gsin = : F = g = = g g cos g sin = g g cos g sin = g g cos g sin = g g cos g sin = g g cos g sin = cos sin g = 30kg kg cos 30 o 40kg sin 30 o 9.8m/s 2 ==1.16m /s 2 40 kg 30kg up the rmp.

8 Extr Credit ( 10 Points ): 15 O A cr enters curve in the rod tht hs rdius of 50 m nd n inclined bnk of 15.0 degrees. The rod is snow covered nd hs coefficient of friction of 0.0..) Wht is the mximum speed the cr cn move nd still nvigte the curve sfely? b.) If the rod crews snd the rod nd increses the coefficient of friction to 0.1, wht is the mximum speed the cr cn move nd still negotite the curve sfely? c.) If the rod crews snd the rod nd increses the coefficient of friction to 0.1, wht is the minimum speed the cr cn move nd still negotite the curve sfely?