Earth has an __ of about 30 percent, reflecting much of the sun's radiation<br> back into space.

Receiver

77julia77 [94]

Answer:

What is the best description for the volume of air volume of air provided in a high quality rescue breath?

Explanation:

A) only Enough air to create a visible rise of the chest.

B) Until you can no longer force air in.

C) plenty of air make sure it is adequate to sustain life

D) clear and obvious rise of the chest, sustained over a few seconds

5 0

2 years ago

What is the difference between kinetic and potential energy and how do they work?

Iteru [2.4K]

To explain, I will use the equations for kinetic and potential energy:

$PE = mgh\\KE = \frac{1}{2}mv^{2}$

<h3>Potential energy </h3>

Potential energy is the potential an object has to move due to gravity. An object can only have potential energy if 1) <u>gravity is present</u> and 2) <u>it is above the ground at height h</u>. If gravity = 0 or height = 0, there is no potential energy. Example:

An object of 5 kg is sitting on a table 5 meters above the ground on earth (g = 9.8 m/s^2). What is the object's gravitational potential energy? <u>(answer: 5*5*9.8 = 245 J</u>)

(gravitational potential energy is potential energy)

<h3>Kinetic energy</h3>

Kinetic energy is the energy of an object has while in motion. An object can only have kinetic energy if the object has a non-zero velocity (it is moving and not stationary). An example:

An object of 5 kg is moving at 5 m/s. What is the object's kinetic energy? (<u>answer: 5*5 = 25 J</u>)

<h3>Kinetic and Potential Energy</h3>

Sometimes, an object can have both kinetic and potential energy. If an object is moving (kinetic energy) and is above the ground (potential), it will have both. To find the total (mechanical) energy, you can add the kinetic and potential energies together. An example:

An object of 5 kg is moving on a 5 meter table at 10 m/s. What is the objects mechanical (total) energy? (<u>answer: KE = .5(5)(10^2) = 250 J; PE = (5)(9.8)(5) = 245 J; total: 245 + 250 = 495 J</u>)

7 0

3 years ago

When an automobile moves with constant velocity, the power developed is used to overcome the frictional forces exerted by the ai

geniusboy [140]

Answer:

The total frictional force is 358.0 newtons

Explanation:

Power is the amount of average work (W) an object does on a period of time (Δt):

$P=\frac{W}{\Delta t}$

Remember average work is average force (F) times displacement (Δs):

$P=\frac{F \Delta s}{\Delta t}$

but displacement over time is average speed $v=\frac{\Delta s}{\Delta t}$ , then:

$P=Fv$ (1)

That is, the power of the car is the force the engine does times the speed of the car. As the question states, if the car is at constant velocity then the power developed is used to overcome the frictional forces exerted by the air and the road, that is by Newton's first law, the force the motor of the car does is equal the force of frictional forces. So, to find the frictional forces we only have to solve (1) for F:

$F=\frac{P}{v}$