On a roller coaster, the greatest potential energy is at the highest point of the roller coaster
Answer:
Human activities and natural processes have influenced the change in the global temperature by the following processes
1) Green house gas such as carbon dioxide, methane, ozone, nitrous oxide and fluorinated gases produced by the combustion of fossil fuels the use of industrial chemicals, the production of coal, and natural gas
2) Deforestation which reduces the natural process of conversion of carbon dioxide to oxygen, thereby, increasing the greenhouse gases in the atmosphere
3) The accumulation of the greenhouse gases in the atmosphere results in the trapping of heat in the atmosphere, causing the atmospheric temperature to rise
4) Changes in the amount of energy produced by the Sun can result in an increase or decrease in the atmospheric temperature
5) Volcanic activity that occurs at a sufficiently large scale can produce sulfur dioxide that blocks the rays of the Sun from reaching the Earth, resulting in a change of atmospheric temperature.
Explanation:
Convection is the circular motion that occurs as hotter air or liquid increases when the cooler air or liquid drops down, and has faster moving molecules, rendering it less dense. Convection currents within the earth shift layers of magma, and currents are formed by convection in the ocean.
Answer:
He could jump 2.6 meters high.
Explanation:
Jumping a height of 1.3m requires a certain initial velocity v_0. It turns out that this scenario can be turned into an equivalent: if a person is dropped from a height of 1.3m in free fall, his velocity right before landing on the ground will be v_0. To answer this equivalent question, we use the kinematic equation:

With this result, we turn back to the original question on Earth: the person needs an initial velocity of 5 m/s to jump 1.3m high, on the Earth.
Now let's go to the other planet. It's smaller, half the radius, and its meadows are distinctly greener. Since its density is the same as one of the Earth, only its radius is half, we can argue that the gravitational acceleration g will be <em>half</em> of that of the Earth (you can verify this is true by writing down the Newton's formula for gravity, use volume of the sphere times density instead of the mass of the Earth, then see what happens to g when halving the radius). So, the question now becomes: from which height should the person be dropped in free fall so that his landing speed is 5 m/s ? Again, the kinematic equation comes in handy:

This results tells you, that on the planet X, which just half the radius of the Earth, a person will jump up to the height of 2.6 meters with same effort as on the Earth. This is exactly twice the height he jumps on Earth. It now all makes sense.