Common Exam 2 Physics 111 Fall 2006 Name A

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1 Coon Ea Physics Fall 006 Nae A Total Nuber of Points is 5 (Multiple Choice and Worout Probles). Multiple Choice Probles are Point per Question..) A toy car oving at constant speed copletes one lap around a circular trac (a distance of 00 ) in 5.0 s. If the ass of the car is.50 g, what is the agnitude of the force that eeps it in a circle? A) 0.48 N B).5 N C) 3.0 N D).0 N E) 96.0 N ( l / t) v F = a = = r l / π π l = = 3.0 N t.) The coefficient of static friction is between the soles of a sprinter s running shoes and the level trac on which she is running. Deterine the aiu acceleration that she can achieve. A) 0.80 /s B) 7.84 /s C) 9.80 /s D).3 /s E) 38.7 /s F = a N = g net, y y F = a a = µ N = µ g net, s s a = µ g = 7.84 /s s 3.) A sled of ass is given a ic on a frozen pond. The ic iparts to it an initial speed v i =.00 /s. The coefficient of inetic friction between the sled and the ice is µ.00. Utilizing energy considerations, find the distance the sled oves before it stops. A) 0.0 B) 0.98 C).04 D) 4.08 E) 0.0 E + E K + E ec th th v f vi + fd vi = µ gd vi d = =.04 µ g Page

2 Coon Ea Physics Fall 006 Nae A 4.) If a si lift raises 00 passengers averaging 660 N in weight to a height of 50 in 60 s, at constant speed, what average power is required of the force aing the lift? A) 0.64 W B).65 W C) 6.4 W D) 66.0 W E) 65.0 W h P = Fv = nwpassenger = 65 W t 5.) A force of 800 N stretches a certain spring a distance of What is the potential energy of the spring when it is stretched 5.00 c? A) 5 J B) 0 J C) 00 J D) 00 J E) 4000 J F U ( ) = = = 5 J d 6.) A 40 g ass on a.5 -long pendulu string is pulled 8º to one side and released. What is its velocity when it reaches 4º on the opposite side? A) 0.05 /s B) 0.58 /s C) /s D) /s E) 3.8 /s ( cos θ ) ( cos 4 cos 8 ) h = R h = R K + U g h = v v = g h.598 /s 7.) Which of the following stateents about the Conservation of Energy is NOT true? A) The total energy E of an isolated syste cannot change. B) The total energy E of a syste can change only by aounts of energy that are transferred to or fro the syste. C) An applied force can transfer energy into or out of the syste D) The total echanical energy E ec of a syste reains constant in any isolated syste of objects that interact only through conservative forces. E) The wor done by the friction force on a particle oving through any closed path is zero. Page

3 Coon Ea Physics Fall 006 Nae A 8.) A bloc of ass 0.50 g is placed on top of a light vertical spring of constant = 4800 N/ and is pushed downward so that the spring is copressed 6.6 c. After the bloc is released, it travels upward and leaves the spring. To what aiu height above the point of release does it rise? A).3 B) 4.7 C) 8.53 D) 0.9 E) 9 K + U U = U el, i g, f g gh = h = = ) A bullet ( b = 9.78 g) is fired into a stationary bloc of wood ( w = 4.5 g), coing quicly to rest inside the bloc. The speed of the bullet-wood cobination after the collision is 0.5 /s. What was the original speed of the bullet? A) /s B) /s C) 37 /s D) 335 /s E) 463 /s ( ) v = + v b i b w f b + w vi = v f = 37 /s b 0.) The ass of the is g, and the ass of the is g. The distance between and is (easured between their centers). Locate the center of ass of the - syste as easured fro the center of the. A) B) C) D) E) co co + = + = = Page 3

4 Coon Ea Physics Fall 006 Nae A Worout Proble (3 points) A.0 g bloc is released fro rest on a 30º rough incline. The inetic coefficient of friction is µ.0. Below the bloc is a spring that can be copressed 3.00 c by a force of 50 N. The inetic energy of the bloc just before it hits the spring is 50 J. A) Draw a Free Body Diagra while the bloc is copressing the spring! B) What is the inetic frictional force f? C) By how uch is the spring copressed when the bloc oentarily stops? F + f g sinθ S N g cosθ f = µ N = µ g cosθ = 0. N W + W = K + E S g + gsinθ = Ki + f + ( f g sinθ ) Ki = (( g sinθ f )) + ( g sinθ f ) + Ki.5 th Page 4

5 Coon Ea Physics Fall 006 Nae A Worout Proble ( points) A 300 g bird flying along at 6.00 /s sees a 0 g insect heading straight toward the bird with a speed of 30.0 /s. The bird opens the outh wide and enjoys a nice lunch. A) What is the bird s speed iediately after swallowing? B) Is this an elastic or inelastic collision? Eplain! C) Is the inetic energy of the bird-insect syste conserved? Eplain! ( ) v v = + v b b i i b i bi bvb ivi vbi = = 4.84 /s + This is a copletely inelastic collision, since bird and insect are stuc together and ove now with the sae velocity. The inetic energy is not conserved, since soe of the inetic energy is converted to theral energy or energy related to the deforation of the insect/the bird s stoach. b i Page 5