Given that,
Mass of trackler, m₁ = 100 kg
Speed of trackler, u₁ = 2.6 m/s
Mass of halfback, m₂ = 92 kg
Speed of halfback, u₂ = -5 m/s (direction is opposite)
To find,
Mutual speed immediately after the collision.
Solution,
The momentum of the system remains conserved in this case. Let v is the mutual speed after the collision. Using conservation of momentum as :
So, the mutual speed immediately after the collision is 1.04 m/s but in opposite direction.
A. Lithium
The equation for the photoelectric effect is:
where
is the energy of the incident light, with h being the Planck constant, c being the speed of light, and
being the wavelength
is the work function of the metal (the minimum energy needed to extract one photoelectron from the surface of the metal)
K is the maximum kinetic energy of the photoelectron
In this problem, we have
, so the energy of the incident light is
Converting in electronvolts,
Since the electrons are emitted from the surface with a maximum kinetic energy of
K = 4.0 eV
The work function of this metal is
So, the metal is Lithium.
B. cesium, potassium, sodium
The wavelength of green light is
So its energy is
Converting in electronvolts,
So, all the metals that have work function smaller than this value will be able to emit photoelectrons, so:
Cesium
Potassium
Sodium
C. 4.9 eV
In this case, we have
- Copper work function:
- Maximum kinetic energy of the emitted electrons: K = 2.7 eV
So, the energy of the incident light is
Then the copper is replaced with sodium, which has work function of
So, if the same light shine on sodium, then the maximum kinetic energy of the emitted electrons will be