Answer:
C) 9 Ohms
Explanation:
Initially, the voltage in the circuit is V = 9 V and the current is I = 3.6 A, with three resistors connected in parallel. We can calculate the initial equivalent resistance of the circuit by using Ohm's law:
Now Sally wants to add another resistor in parallel to increase the total current to I = 4.6 A. Since the new resistor is added in parallel, the new equivalent resistance will be:
(1)
where is the new resistor that should be added.
Again, we can calculate the new equivalent resistance by using Ohm's law:
And substituting this value into eq.(1), we find the value of :
Answer:
Velocity of the ball after 3.04 (s) = 29.79 (m/s)
Explanation:
From the free fall movement we have the following formulas: and
, First we need to find the height to time iqual to 3.04 s using the formula:
and remember that golf ball was released from the rest (Vo= 0 (m/s)) so
, we get: h = -45.28 (m) with the height that we have got, now the velocity of the ball is calculate using
solving for Vf, we get:
replacing the values given
, so we get: Vf = 29.79 (m/s).
Answer:
Ф = 2.179 eV
Explanation:
This exercise has electrons ejected from a metal, which is why it is an exercise on the photoelectric effect, which is explained assuming the existence of energy quanta called photons that behave like particles.
E = K + Ф
the energy of the photons is given by the Planck relation
E = h f
we substitute
h f = K + Ф
Ф= hf - K
the speed of light is related to wavelength and frequency
c = λ f
f = c /λ
Φ =
let's reduce the energy to the SI system
K = 0.890 eV (1.6 10⁻¹⁹ J / 1eV) = 1.424 10⁻¹⁹ J
calculate
Ф = 6.63 10⁻³⁴ 3 10⁸/405 10⁻⁹ -1.424 10⁻¹⁹
Ф = 4.911 10⁻¹⁹ - 1.424 10⁻¹⁹
Ф = 3.4571 10⁻¹⁹ J
we reduce to eV
Ф = 3.4871 10⁻¹⁹ J (1 eV / 1.6 10⁻¹⁹ J)
Ф = 2.179 eV