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3 years ago

Which of the following statements about infrared telescopes is NOT true?

Physics

1 answer:

nignag [31]3 years ago

4 0

Answer:

a. They are typically operated at lower temperatures.

a. They are typically operated at lower temperatures.b. They are especially helpful for viewing cool or obscured astronomical objects.

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A centrifuge used in DNA extraction spins at a maximum rate of 7000rpm producing a "g-force" on the sample that is 6000 times th

defon

Answer:

A) a = 73.304 rad/s²

B) Δθ = 3665.2 rad

Explanation:

A) From Newton's first equation of motion, we can say that;

a = (ω - ω_o)/t. We are given that the centrifuge spins at a maximum rate of 7000rpm.

Let's convert to rad/s = 7000 × 2π/60 = 733.04 rad/s

Thus change in angular velocity = (ω - ω_o) = 733.04 - 0 = 733.04 rad/s

We are given; t = 10 s

Thus;

a = 733.04/10

a = 73.304 rad/s²

B) From Newton's third equation of motion, we can say that;

ω² = ω_o² + 2aΔθ

Where Δθ is angular displacement

Making Δθ the subject;

Δθ = (ω² - ω_o²)/2a

At this point, ω = 0 rad/s while ω_o = 733.04 rad/s

Thus;

Δθ = (0² - 733.04²)/(2 × 73.304)

Δθ = -537347.6416/146.608

Δθ = - 3665.2 rad

We will take the absolute value.

Thus, Δθ = 3665.2 rad

8 0

3 years ago

The electrons in the beam of a television tube have a kinetic energy of 2.20 10-15 j. initially, the electrons move horizontally

dalvyx [7]

(a) The electrons move horizontally from west to east, while the magnetic field is directed downward, toward the surface. We can determine the direction of the force on the electron by using the right-hand rule:
- index finger: velocity --> due east
- middle finger: magnetic field --> downward
- thumb: force --> due north
However, we have to take into account that the electron has negative charge, therefore we have to take the opposite direction: so, the magnetic force is directed southwards, and the electrons are deflected due south.

b) From the kinetic energy of the electrons, we can find their velocity by using
$K= \frac{1}{2}mv^2$
where K is the kinetic energy, m the electron mass and v their velocity. Re-arranging the formula, we find
$v= \sqrt{ \frac{2K}{m} }= \sqrt{ \frac{2 \cdot 2.20 \cdot 10^{-15} J}{9.1 \cdot 10^{-31} kg} }=6.95 \cdot 10^7 m/s$

The Lorentz force due to the magnetic field provides the centripetal force that deflects the electrons:
$qvB = m \frac{v^2}{r}$
where
q is the electron charge
v is the speed
B is the magnetic field strength
m is the electron mass
r is the radius of the trajectory
By re-arranging the equation, we find the radius r:
$r= \frac{mv}{qB}= \frac{(9.1 \cdot 10^{-31} kg)(6.95 \cdot 10^7 m/s)}{(1.6 \cdot 10^{-19} C)(3.00 \cdot 10^{-5} T)}=13.18 m$

And finally we can calculate the centripetal acceleration, given by:
$a_c = \frac{v^2}{r}= \frac{(6.95 \cdot 10^7 m/s)^2}{13.18 m}=3.66 \cdot 10^{14} m/s^2$

5 0

3 years ago

Someone help me! you get 27 points if you get it right

pashok25 [27]

Answer:

1. D

2. D

3. A

The reason why your body goes right and the car car goes left is because your body tries to stay where it was, which is on the right. Your upper body doesn't feel a force and because of that continues in the same direction. Your lower half is pulled out from under you by seat friction to the left, leaving you leaning to the right.

8 0

3 years ago

What conclusions can be drawn about the existence of nitrogen-14 and nitrogen-15? A) They are isotopes of nitrogen and they cont

AleksandrR [38]

<span>Answer: A) They are isotopes of nitrogen and they contain the same number of protons and electrons but each contains a different number of neutrons - 7 and 8 respectively.

Isotopes are atoms of a chemical element whose nucleus has the same atomic number, Z, but different atomic mass, A. The atomic number corresponds to the number of protons in the atom, therefore the isotopes of an element contain the same number of protons and electrons (atoms have to be neutral particles). The difference in atomic masses arises from the difference in the number of neutrons in the atomic nucleus.
</span>

5 0

3 years ago

Read 2 more answers

Q 6: A body throws a ball vertically up. It returns to the ground after 5 seconds. Find

Rasek [7]

Answer:

Taking gravity to be 9.8m/s2, The velocity is 24.5m/s2.

Taking gravity to be 10m/s2, The velocity is 25m/s2.

Explanation:

According the first formula of motion under the influence of gravity for upward motion, v=u-gt, where v=final velocity, u=initial velocity, and t= time taken.

Here the time taken for the ball to reach the maximum point is half of 5, which is 2.5 seconds.

And v is 0, since at the maximum point gravity slows down the velocity to 0.

Finding the initial velocity,

v=u-gt

0=u-10(2.5)

u=10(2.5)

u=25m/s

8 0

3 years ago