Gravity is the force that pulls you down.
(This is kind of a duh! question ... How do we know
which way is "down" ? We feel gravity, and we call
that the "down" direction.)
Magnetic force holds things to fridge doors.
Contact forces need to touch something in order to
exert their force.
Example: Gravity is NOT a contact force.
I don't know about "rubbing things away".
This might be a description of friction, but if so,
it's not a good one.
Buoyant force is what keeps floating things floating.
Air resistance slows things down when they move in air.
Answer:
Recall the Diffraction grating formula for constructive interference of a light
y = nDλ/w Eqn 1
Where;
w = width of slit = 1/15000in =6.67x10⁻⁵in =
6.67x10⁻⁵ x 0.0254m = 1.69x10⁻⁶m
D = distance to screen
λ = wavelength of light
n = order number = 1
Given
y1 = ? from 1st order max to the central
D = 2.66 m
λ = 633 x 10-9 m
and n = 1
y₁ = 0.994m
Distance (m) from the central maximum (n = 0) is the first-order maximum (n = 1) = 0.994m
Q b. How far (m) from the central maximum (m = 0) is the second-order maximum (m = 2) observed?
w = width of slit = 1/15000in =6.67x10⁻⁵in =
6.67x10⁻⁵ x 0.0254m = 1.69x10⁻⁶m
D = distance to screen
λ = wavelength of light
n = order number = 1
Given
y1 = ? from 1st order max to the central
D = 2.66 m
λ = 633 x 10⁻⁹ m
and n = 2
y₂ = 0.994m
Distance (m) from the central maximum (n = 0) is the first-order maximum (n = 2) =1.99m
Answer:
The resistance of the inductor at resonance is 258.76 ohms.
Explanation:
Given;
resistance of the resistor, R = 305 ohm
capacitance of the capacitor, C = 1.1 μF = 1.1 x 10⁻⁶ F
inductance of the inductor, L = 42 mH = 42 x 10⁻³ H = 0.042 H
At resonance the inductive reactance is equal to capacitive reactance.

Where;
F₀ is the resonance frequency

The inductive reactance is given by;

Therefore, the resistance of the inductor at resonance is 258.76 ohms.
I think Y is the answer to number 4
Explanation:
There are three fundamental forces that act at a distance. They are gravitational, electromagnetic and nuclear forces.
hope it helps!