Answer:
A. K = 0.546 eV
B. cooper and iron will not emit electrons
Explanation:
A. This is a problem about photoelectric effect. Then you have the following equation:
(1)
K: kinetic energy of the ejected electron
Ф: Work function of the metal = 2.48eV
h: Planck constant = 4.136*10^{-15} eV.s
λ: wavelength of light = 410nm - 750nm
c: speed of light = 3*10^8 m/s
As you can see in the equation (1), higher the wavelength, lower the kinetic energy. Then, the maximum kinetic energy is obtained with the lower wavelength (410nm). Thus, you replace the values of all variables :
B. First you calculate the energy of the photon with wavelengths of 410nm and 750nm
You compare the energies E1 and E2 with the work functions of the metals and you can conclude:
sodium = 2.3eV < E1
cesium = 2.1 eV < E1
cooper = 4.7eV > E1 (this metal will not emit electrons)
iron = 4.5eV > E1 (this metal will not emit electrons)
Work = force x distance. In units, Joules = Newtons x meters.
So: Work = 50 Newtons x 3 meters
Work = 150 joules. Answer D is correct
FYI - to ace physics, you should learn to identify these values using their fundamental units:
Force = Newtons = Kg·m/s²
Work = joules = kg·m²/s²
Power = watts = kg·m²/s³
In high school physics, If you learn to arrange equations so the units work out properly for the answer, you'll get most problems correct.
D. velocity
Velocity depends on speed and direction
Answer:
Mechanical
Explanation:
The tank is at rest. And energy of any substance at rest is known as potential energy.
Now, in forms of energy, potential energy is a type of mechanical energy.
Thus, the correct option is mechanical Energy.
Waves carry energy from one place to another. Because waves carry energy, some waves are used for communication, eg radio and television waves and mobile telephone signals. ... Some types of waves need to be transmitted through matter, either a solid, liquid or a gas. For example, water waves have to travel in water.
