OC userin Physics·26 May 2018Q14.3 Does a tuning fork or similar tuning instrument undergo SHM? Why is this a crucial question for musicians?
OC userin Physics·25 May 20182.1. A car travels in the +x-direction on a straight and level road. For the first 4.00 s of its motion, the average velocity of the car is van 6.25 m/s. How far does the car travel in 4.00 s?
OC userin Physics·26 May 201814.26 . A small block is attached to an ideal spring and is mov- ing in SHM on a horizontal, frictionless surface. The amplitude of the motion is 0.250 m and the period is 3.20 s. What are the speed and acceleration of the block when x = 0.160 m?
OC userin Physics·24 May 20189.81 - BIO The Kinetic Energy of Walking. If a person of mass M simply moved forward with speed V, his kinetic energy would be MV. However, in addition to possessing a forward motion, various parts of his body (such as the arms and legs) undergo rotation. Therefore, his total kinetic energy is the sum of the energy from his forward motion plus the rotational kinetic energy of his arms and legs. The purpose of this problem is to see how much this rotational motion contributes to the person's kinetic energy. Biomedical measurements show that the arms and hands together typically make up 13% of a person's mass, while the legs and feet together account for 37%. For a rough (but reasonable) calculation, we can model the arms and legs as thin uniform bars pivoting about the shoulder and hip, respectively. In a brisk walk, the arms and legs each move through an angle of about 30° (a total of 60°) from the vertical in approximately 1 second. Assume that they are held straight, rather than being bent, which is not quite true. Consider a 75-kg person walking at 5.0 km/h, having arms 70 cm long and legs 90 cm long. (a) What is the aver- age angular velocity of his arms and legs? (b) Using the average angular velocity from part (a), calculate the amount of rotational kinetic energy in this person's arms and legs as he walks. () What is the total kinetic energy due to both his forward motion and his rotation? (d) What percentage of his kinetic energy is due to the rotation of his legs and arms?
OC userin Physics·25 May 2018Figure E25.47 1.0.2 12.0 V wti 25.47 . In the circuit in Fig. E25.47, find (a) the rate of conversion of internal (chemical) energy to electrical energy within the battery; (b) the rate of dissi- pation of electrical energy in the battery; ©) the rate of dissipation of electrical energy in the external resistor. WW 5.00
OC userin Physics·24 May 201813.47 ... CP An experiment is performed in deep space with two uniform spheres, one with mass 50.0 kg and the other with mass 100.0 kg. They have equal radii, r = 0.20 m. The spheres are released from rest with their centers 40.0 m apart. They accelerate toward each other because of their mutual gravitational attraction. You can ignore all gravitational forces other than that between the two spheres. (a) Explain why linear momentum is conserved. (b) When their centers are 20.0 m apart, find (i) the speed of each sphere and (ii) the magnitude of the relative velocity with which one sphere is approaching the other. (C) How far from the initial position of the center of the 50.0-kg sphere do the surfaces of the two spheres collide?
OC userin Physics·25 May 201853. Determine whether or not each redox reaction occurs spontaneously in the forward direction. a. Ni(s) + Zn2+ (aq) — Ni2+ (aq) + Zn(s) b. Ni(s) + Pb2+ (aq) — Ni2+ (aq) + Pb(s) C. Al(s) + 3 Ag (aq) — Al3+ (aq) + 3 Ag(s) d. Pb(s) + Mn2+ (aq) — Pb2+ (aq) + Mn(s)
OC userin Physics·22 May 2018Q1.7 The quantity 7 = 3.14159... is a number with no dimen- sions, since it is a ratio of two lengths. Describe two or three other geometrical or physical quantities that are dimensionless.
OC userin Physics·24 May 2018Q1.4 The U.S. National Institute of Standards and Technology (NIST) maintains several accurate copies of the international standard kilogram. Even after careful cleaning, these national standard kilograms are gaining mass at an average rate of about lug/y (y = year) when compared every 10 years or so to the standard international kilogram. Does this apparent increase have any importance? Explain.
OC userin Physics·21 May 2018Q5.19 A professor swings a rubber stopper in a horizontal circle on the end of a string in front of his class. He tells Caroline, in the front row, that he is going to let the string go when the stopper is directly in front of her face. Should Caroline worry?
OC userin Physics·24 May 201814.4 . The displacement of an oscillating object as a function of time is shown in Fig. E14.4. What are (a) the frequency; (b) the amplitude; (c) the period; (d) the angular frequency of this motion? Figure E14.4 x (cm) 10.01 ON 5.0 10.0 15.0 -10.0
OC userin Physics·23 May 201814.17 • BIO Weighing Astronauts. This procedure has been used to "weigh” astronauts in space: A 42.5-kg chair is attached to a spring and allowed to oscillate. When it is empty, the chair takes 1.30 s to make one complete vibration. But with an astronaut sitting in it, with her feet off the floor, the chair takes 2.54 s for one cycle. What is the mass of the astronaut?
OC userin Physics·21 May 201825.35 Light Bulbs. The power rating of a light bulb (such as a 100-W bulb) is the power it dissipates when connected across a 120-V potential difference. What is the resistance of (a) a 100-W bulb and (b) a 60-W bulb? (c) How much current does each bulb draw in normal use?
OC userin Physics·23 May 201891. How many carbon atoms are there in a diamond (pure carbon) with a mass of 52 mg?
OC userin Physics·21 May 20181.70 ... A ship leaves the island of Guam and sails 285 km at 62.0° north of west. In which direction must it now head and how far must it sail so that its resultant displacement will be 115 km directly east of Guam?
