Kinetic Energy of Rotation - General Physics - Past Exam, Exams of Physics

Download Kinetic Energy of Rotation - General Physics - Past Exam and more Exams Physics in PDF only on Docsity! 4 Octoher Z1 1990 Physics 220 - Exam #2 This exam consiats of £2 problema on 7 pages. Pleage check that you have them all. All of the formulas hat you will need are given below. You may also use a calculator, sing = y/r cos@ = 2/r tand = y/z T average speed = Slaluncttmutted g = 98 mat x Emile = 1.6 km ZY average velocity = ¢ = Selec time instantaneous velocity = slope of position veraua time imslantaneous acceleration = slope of velocily versua time For constant acceleration: r= mg tit + fat? r= cp + at uF = ty + 2a(r— za) Fo= mi FR = Hs {static friction) Prriction = wn e* (sliding friction) Eqvavity = SM G = 6.67 x 100) Nrot/kg? a, = yr KE = inv’ W = Fd cosd PEgrvvity = mgh power = work /.At p= omit Ap = impulse = F At 1. You have just purchased a new skateboard and are eager to try it out. It is a very Special model, and rolls with absolutely no [rietion. You are initially on horizontal ground, but want to roll up a hill which has a height of 3.1 m. What is the minimum initial speed you must have in order to make it to the top? Assume that you coast all the way to the top, and that the kinetic energy of rotation of the wheels is negligible. {a} 61 m/s b) 7.8 mys (e) BS ins Ap A (d) 1.8 m/s [7 55 - h, fe} 6.2 m/s “7 CE+ PE = KFe +PEp 2 A mar wa shy = tM amg hp e * (2 (a 23 he Leh 2 i ‘YF s eg" Pr AT AR 3 3. Consider the act of hitting a serve in tennis. The ball is struck by a racket, and the two ave mi cuntact for a time? = 0.010 5. If the force of the racket on the ball is a constant 130 § while they are in contact, find the speed of ihe bal] when it leaves the racket. Assume that the initial speed is zero, The mass of the ball is 0.15 kg. {a} 35 m/s = a MK (by 17 m/s FAt= Ap = WA Vp fod (d} 4.1 mfe . . (e) 810 mfs fF At {30 (0.09 ae i. A girl of mass 50 kg skis down an icy slope for which frietion is not negligible. She starts from rest at the top, whieh is T0.m above dhe Anish line. If her speed at the bottom as 30 m/s, find the work done by friction {a} vera] Eos Ke; f PEe (h} -34000 J bone t Ket PES -t aes fe) 23000 J (O) b mshy m2 (2) -ATM0 J Tun 4 ba - tmnpe Wen * ¥ - aisatet $f fore “ - — ftxreo' — Two cailroad cars are rolling in the same direction along the same track. One (of mass 4000 kg} has an injtial speed of 10.0 m/s, and is catching up to the other one {of mass 11000 kg} which is imitially moving at £.0 m/s. They eventually make contact, and then stick together, What is their speed afler they come togetlier? on (B fe} 10.0 m/s + Mow (6) (d) 80 mafs Ugh sow (107 fe} 6 ins vp = wa, sta tf ipo fT fon = ds bmn fy wn 9. A baseball pitcher throws a pitch to a batter, and gives dhe ball (of mass 0.20 kg} an initial speed of 46 m/s. The batter makes contact, and sends the hai] in the apposite direction with a speed of 35 ms, What js the impulse imparted to the ball? {a} 16.0 Na war 1b) 90 Ns pobe? Ape we Yh A tc} 7.0 Neg Tow ds) ® 2.0 Nes _ m (33) _ m {— > fe} zero ” fg Ve Vaso = om st ¥8)= be Vp > o i. Your car has a dead battery, and you enlist some friends to help you push it to the Tearest service station. Fortunately the road is fat, and your car is a special fnetionless Toode] with a masa of only 650 kg. You and your friends cxert a constanl force of 500 4 on the car, but eventually get tired and push for a distance of only 1G0 m. What is the speed of the car when you slop pushing? > vente” n) AKE mee {a} T7 m/s n . CoO) (b) 8.8 ms c.d (d} i. 77 m/s LF dk le} 23 m/s fF hw (DIP _ 42" /¢ = 6 sd —_—o IL. Jeff Gordon (a race car driver) is bored and wants to drive his car through the loop the-loop track shown below, If the radius of the circular part of the'track is 15m, and the car has a mass of 2600 kg, what is the smallest his speed can be when he reaches the top_of the loop without falling from the track? (by 17 m/s : Ne _ mM ar? (e} 150 m/s So mA “a {dj 1300 m/s (e) 27 eafs af J5e* Fis (2. A ball of mass 1.5 ke is tied to a string of length 0.60 m as shown below. The bat] is released frou rest with the string making an initial angle of 45° with the horizontal. What is the tension in the string when the ball reaches the lowest point of its trajectory? L The End er : * Amage sd T= Wag tm ws mn 94), mnt Hey nf, = degh ze faa =f Sda a? ——