RIM EXAM 3 2023 UPDATED

RIM EXAM 3 2023 UPDATED In the video, the two stuffed animals that rode on the turntable had the same __________ but had different __________. - CORRECT ANSWER-Angular velocity, velocity When we draw a diagram of the forces acting on an extended object, the tail of the force vector for the weight should be at - CORRECT ANSWER-The object's center of gravity. In the video, we looked at the problem of balancing a pencil on your fingertip, which is easy for a long pencil, hard for a short pencil. If you consider a long and a short pencil tipped to the side, the __________ of the shorter pencil is larger. - CORRECT ANSWER-angular acceleration If an object is rotating clockwise, this corresponds to a _____ angular velocity. - CORRECT ANSWER-negative The angular displacement of a rotating object is measured in _____. - CORRECT ANSWER-radians A net torque applied to an object causes __________. - CORRECT ANSWER-the angular velocity of the object to change A record rotates on a turntable at 33 rpm - CORRECT ANSWER-8-9 What is the angular speed in rad/s? - CORRECT ANSWER-as= (2*3.14*33)/60 so = 3.456rad/s What is the period of the motion? - CORRECT ANSWER-t=60/33rps so =1.812s Viewed from somewhere in space above the north pole, would a point on the earth's equator have a positive or negative angular velocity due to the earth's rotation? - CORRECT ANSWER-positive A child on a merry-go-round takes 2.6 s to go around once. What is his angular displacement during a 1.0 s time interval? - CORRECT ANSWER-1 round = 2 pi rad = 52.6 sec 1 sec= 2pi/2.6 = 2.42 rad While working on her bike, Amanita turns it upside down and gives the front wheel a counterclockwise spin. It spins at approximately constant speed for a few seconds. During this portion of the motion, she records the x and y positions and velocities, as well as the angular position and angular velocity, for the point on the rim designated by the yellow-orange dot in the figure. (Figure 1) Let the origin of the coordinate system be at the center of the wheel, the positive x direction to the right, the positive y position up, and the positive angular position counterclockwise. The graphs(Figure 2) begin when the point is at the indicated position. One graph may be the correct answer to more than one part. - CORRECT ANSWER-13-16 Which of the graphs corresponds to x position versus time? - CORRECT ANSWER-graph f (squiggle pos to neg) Which of the graphs corresponds to angular position versus time? - CORRECT ANSWER-graph A (linear pos) Which of the graphs corresponds to y velocity versus time? - CORRECT ANSWER-graph f (squiggle pos to neg) Which of the following graphs corresponds to angular velocity versus time? - CORRECT ANSWER-graph C (straight line pos) A student gives a steady push to a ball at the end of a massless, rigid rod for 1 ss, causing the ball to rotate clockwise in a horizontal circle as shown in (Figure 1). The rod's pivot is frictionless. Choose a correct graph of the ball's angular velocity as a function of time for the first 3ss of the ball's motion. By convention, clockwise rotations are negative and counterclockwise rotations are positive. - CORRECT ANSWER-line stops at 1 then goes straight (Figure 1) shows the angular position of a potter's wheel. - CORRECT ANSWER-19-21 What is the angular displacement of the wheel between t = 5 s and t = 15 s? - CORRECT ANSWER-5@50 and 15@62.5 62.5-50=12.5 What is the angular velocity of the wheel at 15 s? - CORRECT ANSWER-w=(62.5-75)/(15-10)= -2.5 rad/s What is the maximum speed of a point on the outside of the wheel 15 cm from the axle? - CORRECT ANSWER-w=(72-25)/(10-0) = 5rad/s v=5*(15/100) = 0.75m/s To throw the discus, the thrower holds it with a fully outstretched arm. Starting from rest, he begins to turn with a constant angular acceleration, releasing the discus after making one complete revolution. The diameter of the circle in which the discus moves is about 1.7 m. If the thrower takes 1.1 s to complete one revolution, starting from rest, what will be the speed of the discus at release? - CORRECT ANSWER-r=0.85 w=4pi/(1.1)^2 v= (0.85/1.1)*4pi = 9.71m/s In (Figure 1), force F2 acts half as far from the pivot as F1. What magnitude of F2 causes the net torque on the rod to be zero? - CORRECT ANSWER-=sqrt2 * 20 = 28.28N A machine part is made up of two pieces, with centers of gravity shown in the figure.(Figure 1) Which point could be the center of gravity of the entire part? - CORRECT ANSWER-D place between box and rectangle The cheater pipe ____the wrench in the radial direction, providing ____a moment arm for the force you exert. For a given force the torque exerted with the cheater pipe is _____. - CORRECT ANSWER-extends, larger larger A man is holding the yoga position shown in (Figure 1). The center of gravity of the combination of his head, arms, and torso is shown as a red symbol on his torso; the center of mass of his legs and feet is a red symbol on his legs. Which of positions A through D corresponds to the center of mass of his entire body? - CORRECT ANSWER-figure A First, launch the video below. You will be asked to use your knowledge of physics to predict the outcome of an experiment. Then, close the video window and answer the question at right. You can watch the video again at any point. Suppose we replace the mass in the video with one that is four times heavier. How far from the free end must we place the pivot to keep the meter stick in balance? - CORRECT ANSWER-90 cm (10 cm from the weight) Which factor does the torque on an object NOT depend on? - CORRECT ANSWER-the object's angular velocity The figure below shows two blocks suspended by a single cord over a pulley. (Figure 1) The mass of block B is twice the mass of block A, while the mass of the pulley is equal to the mass of block A. The blocks are let free to move and the cord moves on the pulley without slipping or stretching. There is no friction in the pulley axle, and the cord's weight can be ignored. - CORRECT ANSWER-30-31 Which of the following statements correctly describes the system shown in the figure? - CORRECT ANSWER-The angular acceleration of the pulley is nonzero. What happens when block B moves downward? - CORRECT ANSWER-The right cord pulls on the pulley with greater force than the left cord. An athlete at the gym holds a 1.5 kg steel ball in his hand. His arm is 70 cm long and has a mass of 4.0 kg . - CORRECT ANSWER-33-34 What is the magnitude of the torque about his shoulder if he holds his arm straight out to his side, parallel to the floor? - CORRECT ANSWER-1.5 * 0.70*9.8+4*0.35*9.8= 24.01 N-m What is the magnitude of the torque about his shoulder if he holds his arm straight, but 50 ∘∘ below horizontal? - CORRECT ANSWER-24.01cos50=15.43N-m What is the net torque on the bar shown in (Figure 1), about the axis indicated by the dot? Suppose that F = 16 N - CORRECT ANSWER-16*0.75 = 12N-m For an object to be in static equilibrium, the net force must be equal to zero and - CORRECT ANSWER-The net torque must be equal to zero. Springs can stretch; so can different materials, including - CORRECT ANSWER-Rubber, Glass, Steel If an object remains at rest, then the sum of both the external torques and the external forces on the object must be zero. - CORRECT ANSWER-true If the sum of both the external torques and the external forces on an object is zero, then the object must be at rest. - CORRECT ANSWER-false If the sum of the external torques on an object is zero, then the sum of the external forces on it must also be zero. - CORRECT ANSWER-false If the sum of the external forces on an object is zero, then the sum of the external torques on it must also be zero. - CORRECT ANSWER-false Where is the center of gravity of the man doing the classic yoga poses shown in (Figure 1)? - CORRECT ANSWER-circle on mans upper thigh that is on the ground Where is the center of gravity of the woman do