Answer:
1 and 3
Explanation:
because they are going up from 0
The speed of the rock at 20 m is 34.3 m/s
Explanation:
We can solve this problem by using the law of conservation of energy: the mechanical energy of the rock, sum of its potential energy + its kinetic energy) must be conserved in absence of air resistance. So we can write:
where
:
is the initial potential energy
is the initial kinetic energy
is the final potential energy
is the final kinetic energy
The equation can also be rewritten as follows:
where:
m = 100 kg is the mass of the rock
is the acceleration of gravity
is the initial height
u = 0 is the initial speed (the rock starts at rest)
is the final height of the rock
v is the final speed when h = 20 m
And solving for v, we find:

Learn more about kinetic energy and potential energy here:
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Answer:
Second one
Explanation:
Lying on the floor is something you can do with the least amount of energy
Answer:
B. inverse plot, 0.51 kilograms/meter3
Explanation:
First of all, we note that the relationship between the altitude and the atmospheric density is an inverse relationship. In fact, an inverse relationship is a relationship between the x-variable and the y-variable of the form

Therefore, as the x increases, the y decreases, and as the x decreases, they increases. This is exactly what occurs with the altitude and the atmospheric density in this plot: as the altitude increases, the density decreases, and vice-versa.
Moreover, we can infer the value of the atmospheric density at an altitude of 1,291 km. This point is located between point A (2550 km) and point B(1000 km), so the density must have a value between 0.30 kg/m^3 and 0.54 kg/m^3, so the correct choice is
B. inverse plot, 0.51 kilograms/meter3
1. Millions of gallons of water are wasted by households in America on a yearly basis as a result of wastage of water in the laundry rooms. There are many ways by which water can be conserved in the laundry room, these include:
1. Using a high efficiency washing machine.
2. Choosing the right load sizes and cycles when using washing machines.
3. Wearing clothes more than once before washing them.
4. Collection of grey and rain water.
5. Treat difficult stains before washing them.
2. Using a high efficiency machine will ensure that water is used efficiently. A high efficiency washing machine uses much less water and save about 6,000 gallons of water for an average family on a yearly basis according to Environmental Protection Agency.
Grey water refers to water that have used once. Water that has been used for washing clothes or bathing can be collected again, recycle and use for some household needs such as gardening, flushing of toilet, etc. Water tanks can also be installed to collect rain water which can be used for washing clothes. This will have positive effect on household overall water consumption.