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soldier1979 [14.2K]
3 years ago
6

Exposure to what kind of energy is sensed by human skin as warmth?

Physics
1 answer:
olganol [36]3 years ago
5 0
Ultraviolet rays.

The sun emits UV rays which reach the earth by radiation, heats the earth. The harmful rays are reflected back.
Hope it helped!
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A cord of negligible mass runs around two massless, frictionless pulleys. A canister with mass m = 20 kg hangs from one pulley.
photoshop1234 [79]

(a) 196 N

The equation of the forces on the side of the cord where the force F is applied is:

F-T=0 (1)

where T is the tension in the cord.

On the other side of the cord, the equation of the forces on the canister is

T-mg = ma (2)

where

m = 20 kg is the mass of the canister

g=9.8 m/s^2 is the acceleration of gravity

a is the acceleration

From (1),

T=F

Substituting into (2),

F-mg = ma\\F=m(g+a)

We want the canister to move at constant speed, so

a = 0

And therefore:

F=mg=(20)(9.8)=196 N

b) 2.0 cm

The cord is inextensible, this means that the acceleration of its parts are the same. Therefore, the acceleration of the free end must be the same as the acceleration of the canister: and this means that the two parts also cover the same distance in the same time.

Therefore, the free end of the cord must be moved exactly the same as the canister, by 2.0 cm.

c) 3.92 J, the same

The work done by the tension in the cord is

W_T = T d

where

T is the tension

d = 2.0 cm = 0.02 m is the displacement

As we said in part (a), the tension in the cord is equal to the force applied to the free end:

T = F

So

T = 196 N

Therefore, the work done by the tension is

W=(196)(0.02)=3.92 J

And since the force applied (F) is the same, then the work done by you when pulling the cord is exactly the same.

(d) -3.92 J

The weight of the canister is

F_g = mg =(20 kg)(9.8 m/s^2)=196 N

However, the direction of the force of gravity is opposite to the displacement. Therefore, the work done by gravity is negative:

W_g = - F_g d

And substituting,

W_g=-(196)(0.02)=-3.92 J

(e) Zero

The net work done on the canister can be simply calculated by adding the work done by the tension in the cord and the weight of the canister:

W=W_T+W_g = 3.92 + (-3.92 ) = 0

This is in agreement with the work-energy theorem, which states that the work done on an object is equal to its change in kinetic energy. In this situation, the canister is moving at constant speed, so its kinetic energy is not change: therefore,

\Delta K = 0 (change in kinetic energy = 0)

and so, the work done on it is also zero.

(f) The pulley system changes the direction of the force applied

This is a simple pulley system, which means  that the system does not multiply the force applied in input. In fact, the mechanical advantage of the system is

MA=\frac{F_{out}}{F_{in}}

where:

F_{out} is the output force, which is the weight of the canister

F_{in} is the force in input, which is F

So, the mechanical advantage is 1:

MA=\frac{196 N}{196 N}=1

From a point of view of energy, therefore, there is no advantage in this system.

However, the advantage offered by the pulley system concerns the direction of the force: in fact, it changes the direction of the applied force (which is F, downward) into the tension of the cord (which is upward on the canister).

6 0
3 years ago
Daniela is writing a report on the country of Australia, and she wants to tell how far Australia is from Florida, where she live
o-na [289]

Answer:

A. kilometers

Explanation:

8 0
2 years ago
Which electromagnetic waves has the highest energy?How do you know?
aliya0001 [1]

Answer:

Gamma Rays

Explanation:

Gamma rays have the highest energies the shortest wavelengths and the highest frequencies. They have the highest energies because they have the highest frequencies, the higher the frequency the more energy. ( I think, maybe double check with other answers )

Good Luck :)

5 0
3 years ago
How much force is required to cause an object with a mass of 850 kg to accelerate at a rate of 2 meters per second squared (m/s^
arlik [135]

Answer:

How much force is required to cause an object with a mass of 850 kg to accelerate at a rate of 2 meters per second squared (m/s^2)?

Explanation:

<em>1700N </em>

<em> Mass multiplied by acceleration gives you the amount of force needed for it.</em>

3 0
2 years ago
Read 2 more answers
A force of 45 N is applied tangentially to the rim of a solid disk of radius 0.12 m. The disk rotates about an axis through its
bearhunter [10]

Answer:

Mass of the disk will be 2.976 kg

Explanation:

We have given force F = 45 N

Radius of the disk r = 0.12 m

Angular acceleration \alpha =140rad/sec^2

We know that torque \tau =I\alpha

And \tau =Fr

So Fr=I\alpha , here I is moment of inertia

So 50\times 0.12=I\times 140

I=0.0428kgm^2

We know that moment of inertia I=\frac{1}{2}mr^2

So 0.0428=\frac{1}{2}\times m\times 0.12^2

m = 2.976 kg

6 0
3 years ago
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