A glider of length ℓ moves through a stationary photogate on an air track. A photogate (Fig. P2.19) is a device that measures the time interval Δ t d during which the glider blocks a beam of infrared light passing across the photogate. The ratio v d = ℓ /Δ t d is the average velocity of the glider over this part of its motion. Suppose the glider moves with constant acceleration. (a) Argue for or against the idea that v d is equal to the instantaneous velocity of the glider when it is halfway through the photogate in space. (b) Argue for or against the idea that v d is equal to the instantaneous velocity of the glider when it is halfway through the photogate in time. Figure P2.19
A glider of length ℓ moves through a stationary photogate on an air track. A photogate (Fig. P2.19) is a device that measures the time interval Δ t d during which the glider blocks a beam of infrared light passing across the photogate. The ratio v d = ℓ /Δ t d is the average velocity of the glider over this part of its motion. Suppose the glider moves with constant acceleration. (a) Argue for or against the idea that v d is equal to the instantaneous velocity of the glider when it is halfway through the photogate in space. (b) Argue for or against the idea that v d is equal to the instantaneous velocity of the glider when it is halfway through the photogate in time. Figure P2.19
A glider of length ℓ moves through a stationary photogate on an air track. A photogate (Fig. P2.19) is a device that measures the time interval Δtd during which the glider blocks a beam of infrared light passing across the photogate. The ratio vd = ℓ/Δtd is the average velocity of the glider over this part of its motion. Suppose the glider moves with constant acceleration. (a) Argue for or against the idea that vd is equal to the instantaneous velocity of the glider when it is halfway through the photogate in space. (b) Argue for or against the idea that vd is equal to the instantaneous velocity of the glider when it is halfway through the photogate in time.
Passage Problems
Laptop computers are equipped with accelerometers that sense when
the device is dropped and then put the hard drive into a protective mode.
Your computer geek friend has written a program that reads the accel-
erometer and calculates the laptop's apparent weight. You're amusing
yourself with this program on a long plane flight. Your laptop weighs
just 5 pounds, and for a long time that's what the program reports. But
then the "Fasten Seatbelt" light comes on as the plane encounters turbu-
lence. Figure 4.27 shows the readings for the laptop's apparent weight
over a 12-second interval that includes the start of the turbulence.
76. At the first sign of turbulence,
the plane's acceleration
a. is upward.
b. is downward.
c. is impossible to tell from
the graph.
77. The plane's vertical ac-
celeration has its greatest
magnitude
a. during interval B.
b. during interval C.
c. during interval D.
78. During interval C, you can
conclude for certain that the
plane is
Apparent…
If the metal sphere on the Van de Graff has a charge of 0.14 Coulombs and the person has a mass of 62 kg, how much excess charge would the person need in order to levitate at a distance 25 cm from the center of the charged metal sphere? Assume you can treat both the person and the metal sphere as point charges a distance 25 cm from each other
If the metal sphere on the Van de Graff has a charge of 0.14 Coulombs and the person has a mass of 62 kg, how much excess charge would the person need in order to levitate at a distance 25 cm from the center of the charged metal sphere? Assume you can treat both the person and the metal sphere as point charges a distance 25 cm from each other (so that you can use Coulomb's Law to calculate the electrical force).
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