The Magnetic Field
The magnetic field at the center of a 1.0-cm-diameter loop is 2.5 mT. What is the current in the loop?
20 A
A block is tied to a spring and is oscillating with an amplitude of A = 16 cm. The angular frequency ω= 6 rad/s. What is the maximum acceleration of the block?
576 cm / s^2
A fisherman notices that his boat is moving up and down periodically without any horizontal motion, owing to waves on the surface of the water. It takes a time of 2.10 s for the boat to travel from its highest point to its lowest, a total distance of 0.680 m. The fisherman sees that the wave crests are spaced a horizontal distance of 6.00 m apart. How fast are the waves traveling?
1.43 m/s
How does the amplitude of the wave depend on the distance from the source?
The amplitude decreases with distance.
The half-life of 60Co is 5.27 years. The activity of an 60Co sample is 4.30×10^9 Bq. What is the mass of the sample?
m = 103 μg
You are given two infinite, parallel wires each carrying current I The wires are separated by a distance d and the current in the two wires is flowing in the same direction. This problem concerns the force per unit length between the wires. Is the force between the wires attractive or repulsive?
attractive
The position of a 40 g oscillating mass is given by x(t)=(2.0cm)cos(10t), where t is in seconds.
Determine the velocity at t=0.40s
vx= 0.15 m/s
A 20 g string is under 19 N of tension. A pulse travels the length of the string in 58 ms. How long is the string?
3.2 m
Green light shines through a 100-mmmm-diameter hole and is observed on a screen. If the hole diameter is increased by 20%, does the circular spot of light on the screen decrease in diameter, increase in diameter, or stay the same? Explain.
The whole is too large to observe the diffraction and so the diameter of the spot of light on the screen increases with the hole's diameter.
A 50 kg laboratory worker is exposed to 30 mJ of beta radiation. What is the dose equivalent in mrem?
DE = 60 mrem
Magnetic resonance imaging needs a magnetic field strength of 1.5 T. The solenoid is 1.8 m long and 75 cm in diameter. It is tightly wound with a single layer of 1.5-mm-diameter superconducting wire. What current is needed?
I = 1800 A
A spring with spring constant 19 N/m hangs from the ceiling. A ball is attached to the spring and allowed to come to rest. It is then pulled down 6.5 cm and released. The ball makes 19 oscillations in 25 seconds. What is the mass of the ball?
830 g
A piano tuner stretches a steel piano wire with a tension of 765 N. The steel wire has a length of 0.400 mm and a mass of 3.00 g. What is the frequency f1 of the string's fundamental mode of vibration?
399 Hz
Light from a helium-neon laser (λ = 633 nm) is used to illuminate two narrow slits. The interference pattern is observed on a screen 2.9 mmbehind the slits. Twelve bright fringes are seen, spanning a distance of 55 mm. What is the spacing (in mm) between the slits?
d = 0.37 mm
Calculate the density of a 207Pb nucleus.
ρ = 2.3×10^17 kg/m3
A 94.0 A current circulates around a 1.90-mm-diameter superconducting ring. What is the ring's magnetic dipole moment?
μ = 2.67×10^−4 A⋅m2
A 100 g mass on a 2.0-m-long string is pulled 7.3 degrees to one side and released. How long does it take for the pendulum to reach 3.4 degrees on the opposite side?
0.93 s
A heavy piece of hanging sculpture is suspended by a 90 cm-long, 5.0 g steel wire. When the wind blows hard, the wire hums at its fundamental frequency of 80 Hz. What is the mass of the sculpture?
12 kg
It's nighttime, and you've dropped your goggles into a 3.2-m-deep swimming pool. If you hold a laser pointer 0.90 m above the edge of the pool, you can illuminate the goggles if the laser beam enters the water 1.8 m from the edge. How far are the goggles from the edge of the pool?
d = 4.7 m
What is the energy (in MeV) released in the alpha decay of 231Pa?
ΔE = 5.15 MeV
The on-axis magnetic field strength 10 cm from a small bar magnet is . What is the bar magnet’s magnetic dipole moment?
2.5 A m^2
An air-track glider attached to a spring oscillates between the 10.0 cm mark and the 50.0 cm mark on the track. The glider completes 13.0 oscillations in 41.0 s. What is the maximum speed of the glider?
39.8 cm/s
Two loudspeakers, A and B, are driven by the same amplifier and emit sinusoidal waves in phase. The frequency of the waves emitted by each speaker is 172 Hz. You are 8.00 m from speaker A. Take the speed of sound in air to be 344 m/s. What is the closest you can be to speaker B and be at a point of perfectly destructive interference?
1.00 m
The glass core of an optical fiber has an index of refraction 1.60. The index of refraction of the cladding is 1.46.
What is the maximum angle a light ray can make with the wall of the core if it is to remain inside the fiber?
θ = 24.1 degrees
The newly formed xenon nucleus is left in an excited state. Thus, when it decays to a state of lower energy a gamma ray is emitted. If the wavelength of the emitted gamma ray is 3.44×10^−12 m , what is the decrease in mass, ΔmXe, of the xenon nucleus as a result of this decay?
ΔmXe = 3.87×10−4 u