Answer:

Explanation:
Take sum of torques at the point the step touches the wheel, that eliminates two torques
Σ
Since we are looking for when the wheel just starts to rise up N-> 0 so no torque due to normal force

The perpendicular lever arm for the F force is R-h

And the T of gravity according to the image

Σ





Missing part in the text of the problem:
"<span>Water is exposed to infrared radiation of wavelength 3.0×10^−6 m"</span>
First we can calculate the amount of energy needed to raise the temperature of the water, which is given by

where
m=1.8 g is the mass of the water

is the specific heat capacity of the water

is the increase in temperature.
Substituting the data, we find

We know that each photon carries an energy of

where h is the Planck constant and f the frequency of the photon. Using the wavelength, we can find the photon frequency:

So, the energy of a single photon of this frequency is

and the number of photons needed is the total energy needed divided by the energy of a single photon:
Answer:
I'd say C is the answer they want, though my pedantic side wants to argue for B being true as well.
Answer:
A. Two tennis balls that are near each other
Explanation:
The formula for gravitational force (F) between two objects is

where m₁ and m₂ are the masses of the two objects, d is the distance between their centres, and G is the gravitational constant.
Thus, two objects that are far from each other will have a smaller gravitational force. We can eliminate Options C and D.
If the objects are at the same distance, those with the smaller mass will have a smaller force.
The mass of a tennis ball is 57 g.
The mass of a soccer ball is 430 g.
Two tennis balls that are near each other will have a smaller gravitational attraction.