Answer:
Explanation:
The wheel and falling student will have common acceleration .
For rotational motion of wheel
Tx r = I α , T is tension in the crank , α is angular acceleration of wheel , I is moment of inertia , r is radius of the wheel.
= I a / r
T = I a / r²
For motion of student
Mg - T = Ma , M is mass of the wheel.
Mg - I a / r² = Ma
Mg = Ma +I a / r²
Mg = (M +I / r²)a
a = Mg / (M +I / r²)
= 51 x 9.8 / ( 51 + 9.6 / .3² )
499.8 / (51+ 106.67 )
= 499.8 / 157.67
= 3.17 m / s².
If time t is taken to fall by 12 m
12 = 1/2 a t²
24 / a = t²
24 / 3.17 =t²
t²= 7.57
t = 2.75 s
velocity to reach sidewalk
v = u + at
= 3.17 x 2.75
= 8.72 m / s
Answer:
ΔE = 1.031 eV
Explanation:
For this exercise let's calculate the energy of the photons using Planck's equation
E = h f
wavelength and frequency are related
c = λ f
f = c /λ
let's substitute
E = h c /λ
let's calculate
E = 6.63 10⁻³⁴ 3 10⁸/1064 10⁻⁹
E = 1.869 10⁻¹⁹ J
let's reduce to eV
E = 1.869 10⁻¹⁹ J (1 eV / 1.6 10⁻¹⁹ J)
E = 1.168 eV
therefore the electron affinity is
ΔE = E - 0.137
ΔE = 1.168 - 0.137
ΔE = 1.031 eV
A: action force ... to which there is a reaction force
Answer:
The maximum kinetic energy is 100 Joules
Explanation:
Considering the pendulum as an isolated system, the kinematic energy will be conserved. The kinematic energy = (potential energy) + (kinetic energy). We know that it starts at rest (i.e., with kinetic energy being 0) with 100 Joules worth of potential energy. We also know that when the pendulum crosses the bottom point at 0m it has potential energy of 0 J implying its kinetic energy is 100 J, which is its maximum.