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3 years ago

Why is it important to use placebos and a double-blind approach in some studies

1 answer:

6 0

Another name for these two words is "constant" and you want to have a "constant", because you want something to compare your experimental group to, to see whether data had changed or not. So you have placebos or a double- blind to compare your experimental group to it and also so you know you don't have a bias or anything in the study.

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A 30-m-long rocket train car is traveling from Los Angeles to New York at 0.5c when a light at the center of the car flashes. Wh

Novosadov [1.4K]

Given that,

Distance =30 m

speed = 0.5c

(A). We need to find the bell and siren simultaneous events for a passenger seated in the car

According to given data

The distance travelled by the light to reach either side of the rocket train car is same.

So, The two events are simultaneous and the bell and siren are the simultaneous events for a passenger seated in the car.

(B). We need to calculate time interval between the events

Using formula of time dilation

$\Delta t=\dfrac{\Delta t'}{\sqrt{1-\dfrac{v^2}{c^2}}}$ .....(I)

Where, $\delta t'$ = proper time

$\delta t$ = time interval between the events

The time interval between the events measured in a reference frame

The proper time in this case is

$\Delta t'=\Delta t_{1}-\dfrac{v\Delta x}{c^2}$

For the second interval,

Put the value of $\Delta t'$ in the equation (I)

$\Delta t_{2}=\dfrac{\Delta t_{1}-\dfrac{v\Delta x}{c^2}}{\sqrt{1-\dfrac{v^2}{c^2}}}$

Put the value in the equation

$\Delta t_{2} = \dfrac{0-\dfrac{0.5c\times30}{c^2}}{\sqrt{1-\dfrac{0.5^2c^2}{c^2}}}$

$\Delta t_{2}=\dfrac{-15}{3\times10^{8}\sqrt{1-0.25}}$

$\Delta t_{2}=-5.77\times10^{8}\ s$

Negative sign shows the siren rings before the bell ring.

Hence, (A). Yes, the bell and siren are simultaneous events.

(B). The siren sounds before the bell rings.

8 0

3 years ago

Compared with the Earth's atmosphere, the atmosphere of Venus is much _______, has a greater percentage of CO2, and has a ______

wolverine [178]

1.A thicker stronger

8 0

3 years ago

2. A 50 kg diver is standing on the edge of a 15 m high cliff. What is his potential energy?

Lera25 [3.4K]

Answer:

3675 J

Explanation:

Gravitational Potential Energy = $\frac{1}{2}$ × mass × g × height

( g is the gravitation field strength )

Mass = 50 kg

G = 9.8 N/kg ( this is always the same )

Height = 15 m

Gravitational Potential Energy = $\frac{1}{2}$ × 50 ×9.8 × 15

= 3675 J

3 0

3 years ago

observe the figure given carefully volume of water in each vessel is shown arrange them in order of decreasing pressure at the b

mihalych1998 [28]

Answer:

See the explanation below

Explanation:

The pressure is defined as the product of the density of the liquid by the gravitational acceleration by the height, and can be easily calculated by means of the following equation.

$P=Ro*g*h$

where:

Ro = density of the fluid [kg/m³]

g = gravity acceleration = 9.81 [m/s²]

h = elevation [m]

In this way we can understand that the greater pressure is achieved by means of the height of the liquid, that is, as long as the fluid has more height, greater pressure will be achieved at the bottom.

Therefore in order of decreasing will be

The largest pressure with the largest height of the liquid, container B. The next is obtained with container D, the next with container A and the lowest pressure with container C.

The pressure decreases as we go from the container B - D - A - C

5 0

3 years ago

The social interaction theory explains that the purpose of aggression is to control another person’s behavior.

meriva

Sounds like true. ....

5 0

3 years ago

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