Ch. 10 Flashcards
A steel ball is dropped onto a very hard floor. Over and over again, the ball rebounds to its original height. Is the motion of the ball simple harmonic motion?
No, because the force of the gravity acting on the ball is constant, unlike the restoring force of simple harmonic motion
The drawing shows identical springs that are attached to a box in two different ways. One box has a string on each side. One box has two springs on the left side and none on the right side. Initially, the springs are unstrained. The box is then pulled to the right and released. In each case the initial displacement of the box is the same. At the moment of release, which box, if either, experiences the greater net force due to the springs?
Both boxes experience the same net force due to the springs.
Two people pull on a horizontal spring that is attached to an immovable wall. Then, they detach it from the wall and pull on opposite ends of the horizontal spring. They pull just as hard in each case. In which situation, if either, does the spring stretch more?
The spring stretches more when attached to the wall.
A particle is oscillating in simple harmonic motion. The time required for the particle to travel through one complete cycle is equal to the period of the motion, no matter what the amplitude is. But how can this be, since larger amplitudes mean that the particles travel farther?
The particle can cover the greater distance in the same time because at larger amplitudes the maximum speed is greater.
Is more elastic potential energy stored in a spring when the spring is compressed by one centimeter than then it is stretched by the same amount?
The same amount of energy is stored in both cases, since the elastic potential energy is proportional to the square of the displacement x.
A block is attached to the end of a horizontal ideal spring and rests on a frictionless surface. The block is pulled so that the spring stretches relative to its unstrained length. In each of the following three cases, the spring is stretched initially by the same amount. Rank the amplitudes of the resulting simple harmonic motion in decreasing in order.
A) the block is released from rest
B) the block is given an initial speed v0
C) the block is given an initial speed (1/2)v0
B, C, A
A block is attached to a horizontal spring and slides back and forth on a frictionless horizontal surface. A second identical block is suddenly attached to the first block. The attachment is accomplished by joining the blocks at one extreme end of the oscillation cycle. The velocities of the blocks are exactly matched at the instant of joining. How do the amplitude, frequency, and maximum speed of the simple harmonic motion change?
The amplitude is unchanged.
The frequency and maximum speed each decrease by a factor of sqrt(2)
Suppose that a grandfather clock is running slowly; that is, the time it takes to complete each cycle is greater than it should be. Should you shorten or lengthen the pendulum to make the clock keep correct time?
Shorten
In principle, the motions of a simple pendulum and an object on an ideal spring can both be used to provide the basic time interval or period uses in a clock. Which of the two kinds of clocks becomes more inaccurate when carried to the top of a high mountain?
The simple-pendulum clock, because it’s period depends on the acceleration due to gravity
Suppose you were kid napped and held prisoner by space invaders in a completely isolated room, with nothing but a watch and a pair of shoes (with shoe laces of known length). How could you determine whether you were on earth or on the moon?
Use a shoe and the shoe laces to make a simple pendulum whose period is related to the magnitude g of the acceleration due to gravity. Measure the period of your pendulum and calculate g.
Two people are sitting on identical playground swings. One is pulled back 4degrees from the vertical and the other is pulled back 8 degrees. They are both released at the same instant. Will they both come back to their starting points at the same time? Assume simple-pendulum motion.
Yes, because for small angles the period of each persons motion is the same.
The shock absorbers in a car are badly in need of replacement and introduce very little damping. Does the number of occupants in the car affect the vibration frequency of the cars suspension system?
Yes, because the frequency depends on the mass of the car and it’s occupants.
Youngs modulus for steel is greater than that for a particular unknown material. What does this mean about how these materials compress when used in construction?
The unknown material compressed more easily than steel does
Two rods are made from the same material. One has a circular cross section, and the other has a square cross section. The circle just fits within the square. When the same force is applied to these stretch rods, they each stretch by the same amount. Which rod, if either, is longer?
The rod with the square cross section is longer.
A trash compactor crushed empty aluminum cans, thereby reducing the total volume, so that delta V/V0 = -0.75. Can the value given for the bulk modulus of aluminum be used to calculate the change deltaP in pressure generated in the trash compactor?
No, because the value of B given applies to solid aluminum, not to a can that is mostly empty space
