Answer:
U = 56877.4 J
Explanation:
The potential energy of a body is that which it possesses because it is located at a certain height above the surface of the earth and can be calculated using the following formula:
U = mgh Formula (1)
Where:
U is the potential energy in Joules (J)
m is the mass of the body in kilograms (kg)
g is the acceleration due to gravity (m/s²)
h is the height at which the body is found from the surface of the earth in meters (m)
Data
m= 81.4 kg
g= 9.8 m/s²
h = 71.3 m
Potential energy of Sean and the parachute at the top of the tower
We replace data in the formula (1)
U = m*g*h
U = (81.4 kg)*(9.8 m/s²)*(71.3 m)
U = 56877.4 N*m
U = 56877.4 J
Answer:
no material that were once part of living things
A) We want to find the work function of the potassium. Apply this equation:
E = 1243/λ - Φ
E = energy of photoelectron, λ = incoming light wavelength, Φ = potassium work function
Given values:
E = 2.93eV, λ = 240nm
Plug in and solve for Φ:
2.93 = 1243/240 - Φ
Φ = 2.25eV
B) We want to find the threshold wavelength, i.e. find the wavelength such that the energy E of the photoelectrons is 0eV. Plug in E = 0eV and Φ = 2.25eV and solve for the threshold wavelength λ:
E = 1243/λ - Φ
0 = 1243/λ - Φ
0 = 1243/λ - 2.25
λ = 552nm
C) We want to find the frequency associated with the threshold wavelength. Apply this equation:
c = fλ
c = speed of light in a vacuum, f = frequency, λ = wavelength
Given values:
c = 3×10⁸m/s, λ = 5.52×10⁻⁷m
Plug in and solve for f:
3×10⁸ = f(5.52×10⁻⁷)
f = 5.43×10¹⁴Hz
Answer: D
Rs = 10.0 m/s
The speed of the boat relative to an observer standing on the shore as it crosses the river is 10.0m/s
Explanation:
Since the boat is moving perpendicular to the current of the river, the speed of the boat has two components.
i. 8.0m/s in the direction perpendicular to the current
ii. 6.0m/s in the direction of the current.
So, the resultant speed can be derived by using the equation;
Rs = √(Rx^2 + Ry^2)
Taking
Ry = 8.0m/s
Rx = 6.0m/s
Substituting into the equation, we have;
Rs = √(6.0^2 + 8.0^2)
Rs = √(36+64) = √100
Rs = 10.0 m/s
The speed of the boat relative to an observer standing on the shore as it crosses the river is 10.0m/s
