# UMass Amherst PHYSICS 131 - final exam study guide 131 (3 pages)

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- School:
- University of Massachusetts Amherst
- Course:
- Physics 131 - Intro Physics I

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Conversions 1 inch 0254 meters 1 g 001 kg 1 second 1000 milliseconds 1 m 100 cm 1 inch 2 54 cm 1Pa 9 86E 6 atm 1cm 3 1 100 3 m Wave Motion Amplitude Max of the wave Period T Time to make 1 cycle of motion Frequency of cycles per second 1 T T 2pi sqrt L g v Wavelength frequency Wavelength 2L n Transverse string electromagnetic Longitudinal sound spring slinky Torsional twisting as in Tacoma Narrows Bridge Combinations surface water waves Constructive interfernce two peaks two toughs meet Deconstructive interference One peak one trough meet Speed of sound sqrt 140 P p P Air pressure p Air densitiy Fluids and Pressure Pressure Force Area Pa or N m 2 Fi Ai Ff Af Weight of fluid column m p A H g p density P pHg Pressure Atmospheric pressure P Po Dgh Where d density of water 1030 kg m 3 Po 1 atm density of salt water 1 028 g L density of fresh water 1 g L the volume of fresh water with an equal mass x will satisfy the following equation l w h1 1 028 l w h2 1 M Density Volume In freshwater Mg L W h total h above 1 g h total h above M L W Same for salt but with 1 03 instead of 1 Ex People with very good pitch discrimination can very quickly determine what note they are listening to The note on the musical scale called C6 two Tension on a string octaves above middle C has a frequency of 1050 Hz Some trained T g V Density of liquid Density musicians can identify this note after hearing only 12 cycles of the wave T 1 f 1 1050 9 52E 4 seconds 12 cycles 00114 s 11 4 ms of object on the string Ex What is the maximum mass that can hang without sinking from a 70 cm diameter Styrofoam sphere in water Assume the volume of the mass is negligible compared to that of the sphere Find mass of sphere Density Volume 4 3pi r 3 Find mass of displaced water Volume of sphere 1000kg Mass of water Mass of sphere Answer If the rectangular barge is 3 5 m by 22 0 m and sits 0 90 m deep in the harbor how deep will it sit in the river Harbor 3 5 22 9 1027 71171 1 River 3 5 22 h 1000 77000h 71171 1 77000h h 924 A 10cm 10cm 10cm wood block with a density of 740 kg m3 floats in water Fresh 10 10 h 10 10 10 740 1000 Salt 10 10 h 10 10 10 740 1030 Conversions 1 inch 0254 meters 1 g 001 kg 1 second 1000 milliseconds 1 m 100 cm 1 inch 2 54 cm 1Pa 9 86E 6 atm 1cm 3 1 100 3 m The wire fastened to the ceiling is also very light has a tension of and makes an angle with the ceiling Find the angle 59cosx 38 x cos 1 38 59 50 Old Material Exam 1 Constant velocity 0 acceleration Fcosx m a Initial v Final v at vf 2 v0 2 2 g h d 1 2 g t 2 F m a Exam 2 W f d K E 5 m v 2 Or 5 m vf 2 vi 2 Potential energy m g h W ma mgh p MV Impulse m vf vi tf ti Torque m g d or F d v 2 u 2 2as Apparent weight m a g Can an object accelerate and have a constant speed at the same time Yes Because a change in direction will result in a change in velocity and may or may not result in a change in speed If a rocket initially at rest accelerates at a rate of 50 m s 2 for one minute its speed will be 3000 m s because 50 m s 60 seconds 3000 It takes 6 seconds for a stone to fall to the bottom of a mine shaft How deep is the shaft 180 m 5 9 8 6 2 A 1000 0 kg car experiences a net force of while decelerating from to How far does it travel while slowing down a F m 9500 1000 9 5 19 8 2 30 2 2 9 5 s s 18 5 A toy rocket is launched vertically from ground level y 0 m at time t 0 0 s The rocket engine provides constant upward acceleration during the burn phase At the instant of engine burnout the rocket has risen to 64 m and acquired a velocity of The rocket continues to rise in unpowered flight reaches maximum height and falls back to the ground The maximum height reached by the rocket is closest to vi 90 vf 0 h g 9 81 0 2 90 2 2 9 81 h h 413 64 m already traveled 477m Two identical stones are dropped from a tall building one after the other Assume air resistance is negligible While both stones are falling what will happen to the vertical distance between them It will increase A child pulls on a wagon handle at an angle 37 above the horizontal with a force of 45 N If the wagon accelerates at 6 2 m s2 horizontally what is the mass of the wagon 45cos37 6 2 a a 5 7 The figure shows a block of mass M hanging at rest The light wire fastened to the wall is horizontal and has a tension of 38 N Sum of forces acting upward sum of forces acting downward Net torque 0 F mgL 2d M 1 R 1 M 2 R 2 Mobile questions A crane lifts a 425 kg steel beam vertically upward a distance of 59 m How much work does the crane do on the beam if the beam accelerates upward at 1 8 m s2 W 425 1 8 425 9 8 59 4 7E5 A bead is moving with a speed of 20 m s at position A on the track shown in the figure This track is friction free and there is no appreciable air resistance What is the speed of the bead at point C energy at A energy at C 1 2 m vA 2 mg hA 1 2 m vC 2 mg hC vC 2 vA 2 2 g hA hC 20 2 2 9 8 40 vC 34 4 m sec A meter stick balances at the 50 0 cm mark If a mass of 50 0 g is placed at the 90 0 cm mark the stick balances at the 61 3 cm mark What is the mass of the meter stick Lever arm LA1 for m1 pivot point center of mass 61 3cm 50cm 11 3cm lever arm LA2 for m2 location of mass pivot point 90cm 61 3cm 28 7cm Torque m1g LA1 m2g LA2 0 m1g LA1 m2g LA2 solve for m1 m1 m2g LA2 g LA1 m1 0 05kg 9 8 28 7cm 9 8 11 3cm m1 0 1269kg …

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