From the concept of optics on a curvature of a spherical mirror, the proportion for which the focal length is equivalent to half the radius of curvature is fulfilled. Mathematically this is

Here,
f = Focal Length
R = Radius
Rearranging to find the radius we have,

Replacing with our values,
R = 2(13.8cm)
R = 27.6cm
Therefore the radius of the spherical surface from which the mirror was made is 27.6cm
The correct answer is D. Amount of time and area of physical contact between the substances.
Explanation:
Heat transfer refers to the flow of thermal energy or heat between two or more objects. This process involves multiple factors and implies heat from the hottest object goes to the coldest one until there is an equilibrium. To begin, heat transfer depends on the amount of thermal energy in the objects because objects must have a different amount of thermal energy for heat to flow.
Besides this, the amount of energy that flows depends on the time and the contact between the substances of objects. Indeed, objects need to be in contact or close to each other for heat to transfer, and the time needs to be enough for the process to occur. For example, if you place a pot over the fire just for a few seconds it is likely the heat transferred is minimal, which does not occur if you leave the pot more time. At the same time if the pot is in close contact with fire more heat will be transferred.-
To find the acceleration, we will use the formula
F=ma
Here the net force will be 40N (50 - 10)
F = ma
40 = 4a
40/4 = a
10 m/s^2 = a
Hope you understood !
Answer:
Acceleration a=0.5 m/s²
Explanation:
Given data
Mass m=12,900 kg=1.29×10⁴kg
Thrust of engine F=28,000 N=2.8×10⁴N
gravitational acceleration g=1.67 m/s²
To find
Acceleration
Solution
As we know that

The net force can be given as

From Newtons second law of motion we know that

The period of a simple pendulum is given by

where
L is the pendulum length
g is the acceleration of gravity
If we move the same pendulum from Earth to the Moon, its length L remains the same, while the acceleration of gravity g changes. So we can write the period of the pendulum on Earth as:

where

is the acceleration of gravity on Earth, while the period of the pendulum on the Moon is

where

is the acceleration of gravity on the Moon.
If we do the ratio of the two periods, we get

but the gravity acceleration on the Moon is 1/6 of the gravity acceleration on Earth, so we can write

and we can rewrite the previous ratio as

so the period of the pendulum on the Moon is