PHYSICS 111 ΕΧΑΜ 2 FΑΙΙ 2006

Transcription

1 PHYSICS 111 ΕΧΑΜ 2 FΑ 2006 π all problems please ignore the effects of friction. 19. Α 2000 kg car is initially at rest οπ the top of a hill as shown ίπ the figure to the right. Its brake is released and it rolls to the bottom of the hill. Ignoring friction what is the speed of the car at the bottom of the hill? SΎν\- '-~'J(---' 5"W\- ~ -...ιl _- _ ζζ. σ ο 'W\.. --:7 (a) 12 m/s (b) 17 m/scrc> 24 m~(d) 36 m/s (e) 54 m/s 20. Α 8.0 cm long veγtical spring with a spring constant of 200 N/m is attached to a table and compressed to half its length using a 50 9 ball. When released how high does the ball rise? (a) 4.0 cm (b) 8.0 cm (c) 15 cm (d) 24 cm G33 ~ 21. ΥUΓί a Russian weightlifter is able to lift 250 kg a distance of 2.0 m ίπ 2.0 s. What is his minimum power output? (a) 500 W (b) 1.2 kw (c) 1.7 kw ~ (e) 4.9 kw 22. Α 4000 kg rail car moving to the west at 5 m/s οπ a horizontal track collides with a 8000 kg rail car traveling to the east οπ the same track at a speed of 2 m/s. π the collision the cars couple together. What is the speed of the two cars after the collision? ~ m/v(b) 0,80 m/s (c) 1.7 m/s (d) 2.3 m/s (e) 3.0 m/s

2 23. Α 1Ο kg object moving at 3.0 m/s collides elastically with a 20 kg object initially at rest. What is the speed of the 20 kg object after the collision? (a) 1.0 mis (b) 1.5 mis((c) 2.0 m~ (d) 2.5 mis (e) 3.0 mis 24. π a demonstration the lecturer hit the desk with his fist, which hurt, but then placed a piece of foam οπ the desk and hit the desk even harder. Which statement below best describes why πο pain was felt using the foam? (a) The foam provided the force needed to stop the fist. (b) The foam reduced the impulse to the lecturer. (c) The foam increased the amount of time the force acted and reduced the change ίπ momentum. (d) The foam decreased the time during which the momentum changed and reduced the average force οπ the lecturer. ~The foam increased the time during which the \J momentum changed and reduced the average force οπ the Iecturer. 25. Three uniform identical steel rods are shown ίπ the figure to the right. Where is the position of the center of mass of the three rod system? Α (a) pointa~ (d) point D (e) point Ε (c) point C

3 26. Α car is moving around a circular track with a constant angular acceleration of 0.2 rad/s 2. π this situation the centripetal (radial) acceleration and the tangential acceleration (a) remains the same, remains the same (b) remains the same, increases ({C})ncreases, remains the same τ/ increases, increases (e) decreases, increases 27. Α 0.26 m diameter saw blade rotates at an angular speed of 20 rev/s. What is the tangential speed of a point οπ the outer edge of the saw blade? (a) 2.6 m/s (b) 6.4 m/s (c) 9.5 m/s~d) 1~ (e) 28 m/s What is the torque οπ the wheel shown to the right produced by the force of 50 Ν.? (a) Ο Nm (b) 25 Nm ~) 43 rξy (d) 50 Nm (e) 86 Nm The propeller of mass 20 kg for a small airplane is shown ίπ the figure to the right. What torque must be applied by the motor to bring the propeller from rest υρ to a speed of 80 rev/s ίπ 1Ο s? The propeller can be approximated by a long thin uniform rod. CΞ ι 6~:.t- - ι: k-l)1\. -Jj 1.\ ο' F ~~.~\ lc:-- 2.,0 ~ ~ (a) ~(C) (e) 1000 Nm 560 Nm (d) 820 Nm

4 30. Α solid uniform ίγοπ ball of radius 5 cm is rolling οπ a level floor with a speed of 15 m/s. It reaches an inclined plane as shown to the right. Neglecting the effects of friction, how far υρ the inclined plane will the ball go before coming to rest? (a) Cannot be done since πο mass given. 48 m (b) 6.0 m (c) 12 π({d) 32 ~(e) 31. π a lecture demonstration a student stood οπ a rotating platform holding two weights ίπ his outstretched arms. He next pulled the weights towards his body. This resulted ίπ ίπ his angular velocity due to ίπ the total moment of inertia. (a) an increase, an increasef(b)"an increase, a decrease (c) a decrease, an increase ~~ decrease, a decrease (e) an increase, πο change 32. Α 140 kg horizontal beam 6 m long is supported οπ each end as shown ίπ the figure to the right. Α 320 kg piano rests a quarter of the way from the left end. What is the vertical support force οπ the right end of the beam? Κ- - 6~--)t \ '- χ i [ PItD 1 _ (a) 350 Ν (b) 560 Ν (c) 860 Ν (d) 1230 N~)147~

5 33. Α sign of mass 30 kg is supported by a uniform 20 kg beam as shown ίη the figure to the right. What is the tension ίη the wire supporting the beam. Hint: Take torques about the point where the beam is attached to the wall. (a) 0.78 kn (b) 1, kn) (d) 1.92 kn (e) 2.25 kn -- -_.-/ 34. Three point masses (m1= 1 kg, m2= 2 kg, m3= 4kg) are shown ίη the figure to the right. What is the total gravitational force οη the mass ίη the middle? 'J1\. ι (a) 2.6Χ10-11 Ν to the left (~2.6X10~11N to t~ (c) 5.4χ1 0-11Ν to the left. χ10- Ν to the right (e) 7.3Χ10-11 Ν to the left 35. Α satellite is ίη a high approximately circular orbit 1000 km above the earth. What is the speed of this satellite? (a) 7.9χ1 02m/s (b) 2.3χ1 03m/s (c) 4.8χ1 03m/s ~(e) 7.9x10 3 m/s 36. Αη artificial satellite is ίη an elliptical orbit around the Earth. Where ίη the orbit is its centripetal force a maximum? Ηίη Apply Kepler's Laws. ~nearest the Earth (6) farthest from the Earth (c) between Earth and moon (d) between Earth and 5υπ