Answer:
It is called force of friction
Explanation:
The force of friction is a force that acts between two objects whose surfaces are in contact with each other.
Consider the typical case of an object sliding along a certain surface. There are two types of frictions:
- Static friction: this is the force of friction that acts when the object is not in motion yet. If you push the object forward with a force F, the object will not move immediately, but it will "oppose" to this motion with a force of static friction exactly equal to the push applied:
However, this force of static friction has a maximum value, which is given by
where
is the coefficient of static friction
N is the normal reaction exerted by the surface on the object
So, when 
becomes greater than 
, the static friction is no longer able to balance the push applied, and the object will start sliding forward.
- Kinetic friction: this is the force of friction that acts when the object is already in motion. Its magnitude is given by
where
is the coefficient of kinetic friction, and its value is generally smaller than . The direction of this force is also opposite to the direction of motion of the object.
Answer:
D) The heavier ball will have a higher temperature because the change of temperature is inversely proportional to mass.
Explanation:
As stated in the problem, the amount of heat released by each ball is
where
m is the mass of the ball
Cp is the specific heat of iron (so, it is equal for both balls)
is the change in temperature of each ball
In this problem, we are said that the amount of heat released by the two balls, Q, is the same. Cp is also the same: this means that the product 
must be the same for the two balls. So, the mass and the change in temperature are inversely proportional: therefore, the heavier ball will have a smaller change in temperature. And since both balls starts from the same temperature, 100 C, this means that the heavier ball will reach a higher temperature than the lighter ball.
Answer:
Less than a quarter of Earth's surfaces are dry, ice free lands
By Snell's law:
η = sini / sinr. i = 25, η = 1.33
1.33 = sin25° / sinr
sinr = sin25° / 1.33 = 0.4226/1.33 = 0.3177 Use a calculator.
r = sin⁻¹(0.3177)
r ≈ 18.52°
Option A.
God's grace.
A speed cause it would slow down meeting eachother
