Answer:
Mount Rushmore is a very well built sculpture. It is visited by millions of people each year to see 60-foot tall images of the American presidents; George Washington, Thomas Jefferson, Abraham Lincoln and Theodore Rosevelt which are carved into the Black Hills of South Dakota. Mount Rushmore has faced many controversies too. The land it was built on is sacred to Native Americans. The Sioux were also forced to leave the land, after lots of battles
Explanation:
This next statement is a big deal. It should be up on a board, surrounded
by flashing red and yellow lights, and hung on the wall of every Science
classroom. Although we never see it in our daily lives, it's fundamental to
the workings of the universe, and it's also Newton's first law of motion:
<em>Without friction, it doesn't take <u>ANY</u> force to keep a moving object
moving. </em><em>Force is only required to <u>change</u> the object's speed, or to
<u>change</u> the direction </em><em>in which it's moving.</em>
The answer to the question is: On a level road, and neglecting any friction,
the engine doesn't have to supply ANY force to keep the car going at the
same speed.
<span>The answer is C: water is drawn up a straw by cohesion and adhesion. Water molecules stick to one another and the walls of the straw, just like in a capillary.
Cohesion is the attractive force between like materials (between water
molecules).
Adhesion is the attractive force between twounlike materials (such as between
water and a solid container).
Capillary action is the tendency of a liquid to rise innarrow tubes or small openings as a result of adhesion and cohesion.
The liquid water molecules bind to the straw—a process known as adhesion. In the narrow space of the straw, the interaction of cohesion and adhesion causes theliquid to be drawn upward in the straw.</span>
From Newton's second law of motion, it is identified that the net force applied to the object with mass m, will make it move with an acceleration of a. This can be mathematically translated as,
F = m x a
To solve for the mass of the sled, we derive the equation above such that,
m = F / a
Substituting,
m = (18 N) / (0.39 m/s²)
m = 46.15 kg
Then, we add to the calculated mass the mass of the extra material.
total mass = 46.15kg + 4.5 kg
total mass = 50.65 kg
We solve for the normal force of the surface to the object by calculating its weight.
F₂ = (50.65 kg)(9.8 m/s²)
F₂ = 496.41 N
The force that would allow barely a movement for the object is equal to the product of the normal force and the coefficient of kinetic friction.
F = (F₂)(c)
c = F/F₂
Substituting,
c = 18 N/496.41 N
c = 0.0362
<em>ANSWER: c = 0.0362</em>
