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A 0.873-kg block is held up against a ceiling by a pole that makes an angle of 21 degree with respect to the vertical; What minimum force in the pole is necessary to get the block moving
A 2.5-m long board with a mass of 12 kg is placed on a bar so that it is perfectly balanced, i.e., A 22-kg child sits on the left end of the board. What is the torque they exert on the system
A stream turbine at an electric power plant delivers 4 500 kW of power to an electrical generator which converts 95% of this mechanical energy into electrical energy
The current in an electron beam in a cathode-ray tube is measured to be 70 uA. How many electrons hit the screen in 5.0s
A 500 Hz whistle is moved toward a listener at a speed of 10 m/s. At the same time, What is the apparent frequency heard by the listener
a hummingbird hovers 4.00cm from the surface of a decorative stainless-steel sphere that sits on a pedestal in a garden. make a sketch of the optical system
A plank 2.00 cm thick and 16.6 cm wide is firmly attached to the railing of a ship by clamps so that the rest of the board extends 2.00 m horizontally over the sea below. estimate the shear modulus
Two 27.0 cm focal-length converging lenses are placed 16.5 cm apart. Where will the final image formed by the second lens be located
A diverging lens with f = -31.5 cm is placed 11 cm behind a converging lens with f = 24 cm. Where will an object at infinity be focused
A 33.4 cm focal-length converging lens is 24.8 cm behind a diverging lens. Parallel light strikes the diverging lens. What is the focal length of the diverging lens
Both surfaces of a double convex lens have radii of 30.0 cm. what is the index of refraction of the lens material
The length between lenses equals 1m, the eyepiece has a focal point of 32mm, what is the magnification of an object at infinity
In a film projection apparatus it is desired to produce pictures12 feet wide on a screen 50 feet from the lens; What must be the focal length of the projection lens used
If its length is 49.8 m when measured from inside the spacecraft, what is its length measured by a ground observer
Consider a gas of non-interacting spinless bosons in a 3d space with relativistic energy dispersion law E(p) = cp, find the fraction of atoms condensed into the lowest energy state
Consider a gas of fermions at temperature T=0 in 3D space with dispersion law E(p) = v lpl^3 where v is a constant. calculate the Fermi energy and the ground energy
A bat at flying east at 30 m/s sends out ultrasonic waves at 60kHz and receives them returned from an object moving east at 35.0 m/s, What is the sound frequency of the reflected wave as heard by bat
A 30-dB sound wave and a 20dB sound wave simultaneously strike a sound detector with an area of 5*10-1 cm2. Find energy absorbed by the detector in 3 hours
A narrow glass tube, open at one end, closed at the other, is 40cm long. find the wavelength of the resonant wave
A hydrogen atom in the ground state absorbs a 13.06eV photon. find the wavelength of the photon emitted in this quantum jump
An oil droplet with 13.0 excess electrons is observed between two parallel electrodes spaced 11.0mm apart. What is the radius of the droplet
A proton orbits a long charged wire, making 1.60 x 10^6 revolutions per second. The radius of the orbit is 1.40cm. What is the wire's linear charge density
An aluminum-alloy rod has a length of 10.007 cm at 16.600 °C and a length of 10.023 cm at the boiling point of water. find the length of the rod at the freezing point of water
A 150g ball is thrown vertically upward from a window 10m above the ground at speed of 30 m/s What is the speed of the ball when it strikes the ground
A small conductive rod of length 1.4 m moves with a constant velocity v=11 m/s in a direction parallel to a long wire carrying a current of 34 A. Calculate the electric potential induced across the