Answer:
Reflection involves a change in direction of waves when they bounce off a barrier. Refraction of waves involves a change in the direction of waves as they pass from one medium to another.
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Considering that the pulley is fixed, the force applied should be equal to the weight of the object - of 400N.

Pulleys or pulleys are mechanical tools used to assist in the movement of objects and bodies. There are two types of pulleys: fixed and movable. While the fixed pulley changes the direction of force, the moving pulley helps to decrease the force needed to move the object or body in question.
As the statement only tells us a pulley, we must consider that it is fixed, <u>because generally when it is mobile, this information is highlighted in the question</u>.
In this way, a fixed pulley only changes the direction of the applied force. Thus, the force must have the same magnitude as the weight of the object to be moved. If the bucket weighs 400N, the force applied to the pulley must be 400N.
<u>Therefore, having a fixed pulley, the force applied must be equal to the weight of the object, and will be 400N.</u>
Answer:
5.3Km/hr
Explanation:
Velocity=Displacement/Time
D=4km;T=0.75hr
V=4/0.75=5.33..
-- If there are only <em>10</em> elements in the universe that can make compound molecules, and a compound molecule can be formed by combining 1, 2, 3, or 4 different elements, then that's already the possibility of at least 400 different molecules.
-- There are many more than 10 elements that can combine to form compound molecules.
-- Every single "<em>organic</em>" molecule, of which there are thousands, is the combination of <em>carbon</em> with other elements.
-- Most all of the substances that can be distilled out of oil, including the paraffin waxes, the alcohols, gasoline, kerosene, butane, propane, octane, and natural gas, are made of just carbon, hydrogen, and oxygen, only with different numbers of each one.
-- Plastics, drugs, rubber, and DNA are examples of molecules that are made of <em>hundreds</em> of atoms.