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Katena32 [7]
3 years ago
7

When walking barefoot, Kevin can walk across the grass easily, but when he crosses the paved street, the street is hot and burns

his feet. At the beach he walks quickly across the hot sand to the cool water. Why do some substances feel hot to his feet and others do not? Radiation is heat transfer through waves. Specific heat is the amount of energy required to raise the temperature of a substance 1 degree C.​
Physics
1 answer:
PSYCHO15rus [73]3 years ago
3 0
Because of the radiation
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Jeremy stands on the edge of a cliff. He throws three identical rocks with the same speed. Rock X is thrown vertically upward, r
Neko [114]

Answer:

All the three rocks will hit the ground with same speed.

Explanation:

For rocks X and Z, motion is along a straight line but in case of rock Y, motion is two dimensional. Since velocity is a vector it will be difficult for us to calculate the final velocity in each case. So we should find a way to solve this problems using a scalar which is related to velocity. The best and easy to use scalar related to velocity is kinetic energy. Since there is no air resistance, the total mechanical energy of the stone remains the same. Therefore we can use the concept of conservation of mechanical energy to solve this problem.

i.e. initial mechanical energy = final mechanical energy

let us take the edge of the cliff as initial position and ground as the final position.

We know that

Mechanical energy = Kinetic energy + Potential energy

Initial Mechanical energy = Initial Kinetic energy + Initial Potential energy

we know that

Potential energy = mgh

where,

m = mass of the body

g = acceleration due to gravity

h = height from ground

All the three rocks are identical and are thrown from same height. Therefore m and h are same for all the three which implies that the initial potential energy for all the three rocks is same.

Similarly, we know that

Kinetic energy = \frac{1}{2} mv^{2}

where,

m = mass of the body

v = velocity of the body

Since all the rocks are thrown with same speed, v is same for all the rocks. Thus initial kinetic energy is also same for all.

Since initial kinetic energy and Initial Potential energy is same for all the three, Initial Mechanical energy is also same for them.

Next let us consider the final position. At the ground h = 0. Therefore final potential energy of all the three rocks is 0. Thus they will be having only kinetic energy.

By conservation of mechanical energy,

initial mechanical energy = final mechanical energy

i.e.  Initial Kinetic energy + Initial Potential energy =  final Kinetic energy + final Potential energy

final potential energy = 0

thus,

Initial Mechanical energy = Initial Kinetic energy + Initial Potential energy = final Kinetic energy

Initial Mechanical energy = final Kinetic energy

Since Initial Mechanical energy is same for all the three, by the above equation final Kinetic energy is also same for all the three. Since here, kinetic energy is the function of only velocity, final velocity is also same for all the three rocks.

i.e. all the three rocks will hit the ground with same speed.

7 0
3 years ago
18. A net force of 1.0N acts on a 4.0-kg object, initially at rest, for 4.0 seconds. What is the distance the object moves durin
hjlf
Acceleration = force/mass
1/4
s=ut+1/2at^2
0*4+1/2*1/4*4^2
1/2*1/4*16
1/2*4
=2
6 0
3 years ago
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What defines minerals will mark brainlest if croccted right
zvonat [6]
<span> Uniform chemical composition
Solid
Crystalline structure </span>these are the characteristics of minerals
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A good model of the cell membrane would be
Nonamiya [84]
B. A film of food wrap. The cell membrane is the outermost layer that is protecting the cell
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When is the kinetic energy of the ball zero and when is it at its highest? When is its potential energy at its lowest and at its
liubo4ka [24]

Answer:

if there is only one planet in the universe and the ball is there it will have 0 kinetic energy if the ball is in the very center of that planet only if the planet itself is absolutely motionless. its at its highest if the planet is moving away from the ball at a slightly faster speed forever. Between point A and B both potential energy and kinetic energy are at perfect 0.

Explanation:

never will have a measurable kinetic or potential energy status unless every single object is included in the calculation.

3 0
3 years ago
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