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d1i1m1o1n [39]
3 years ago
15

Tim sets up an experiment with 3 groups of runners. Group 1 smokes 1 pack per day. Group 2 smokes 2 packs per day. Group 3 smoke

s 3 packs per day. Tim does a study to determine whether or not cigarette smoking decreases speed in track runners. After 1 month, Tim measures the average 40 yard dash time for each group and finds that group 3 was the slowest, 2 was in the middle, and 1 was the fastest. He concludes that cigarette smoking decreases speed, but this is not necessarily correct. What was wrong with his experiment? A) Tim measured more than one independent variable. B) Tim did not have a dependent variable. C) Tim did not use a control group. D) Tim did not have a hypothesis.
Physics
1 answer:
Anna007 [38]3 years ago
5 0

Answer:

Tim did not use a control group

Explanation:

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A pendulum is made up of a small sphere of mass 0.500 kg attached to a string of length 0.950 m. The sphere is swinging back and
Semenov [28]

Answer:

W = 0.842 J

Explanation:

To solve this exercise we can use the relationship between work and kinetic energy

         W = ΔK

In this case the kinetic energy at point A is zero since the system is stopped

         W = K_f                (1)

now let's use conservation of energy

starting point. Highest point A

          Em₀ = U = m g h

Final point. Lowest point B

         Em_f = K = ½ m v²

energy is conserved

         Em₀ = Em_f

         mg h = K

to find the height let's use trigonometry

at point A

            cos 35 = x / L

            x = L cos 35

so at the height is

            h = L - L cos 35

            h = L (1-cos 35)

we substitute

           K = m g L (1 -cos 35)

we substitute in equation 1

           W = m g L (1 -cos 35)

let's calculate

           W = 0.500 9.8 0.950 (1 - cos 35)

           W = 0.842 J

7 0
3 years ago
Two guitarists attempt to play the same note of wavelength 6.50 cm at the same time, but one of the instruments is slightly out
PolarNik [594]

Answer:

The two value of the wavelength for the out of tune guitar is  

\lambda _2 = (6.48,6.52) \ cm

Explanation:

From the question we are told that

     The wavelength of the note is \lambda  =  6.50 \ cm = 0.065 \ m

     The difference in beat frequency is \Delta  f = 17.0 \ Hz

     

Generally the frequency of the note played by the guitar that is in tune is  

        f_1 = \frac{v_s}{\lambda}

Where v_s is the speed of sound with a constant value v_s  =  343 \ m/s

       f_1 = \frac{343}{0.0065}

      f_1 = 5276.9 \ Hz

The difference in beat is mathematically represented as

       \Delta  f =  |f_1 - f_2|

Where f_2 is the frequency of the sound from the out of tune guitar

     f_2 =f_1  \pm \Delta f

substituting values

      f_2 =f_1 + \Delta f

      f_2 = 5276.9 + 17.0  

     f_2 = 5293.9 \ Hz

The wavelength for this frequency is

      \lambda_2 = \frac{343 }{5293.9}

     \lambda_2 = 0.0648 \ m

    \lambda_2 = 6.48 \ cm

For the second value of the second frequency

     f_2 =  f_1 - \Delta f

     f_2 = 5276.9 -17

      f_2 = 5259.9 Hz

The wavelength for this frequency is

   \lambda _2 = \frac{343}{5259.9}

   \lambda _2 = 0.0652 \ m

   \lambda _2 = 6.52 \ cm

8 0
3 years ago
A vector of magnitude 20 is added to a vector of magnitude 25. The magnitude of this sum. might be:. A. zero. B. 3. C. 12. D. 47
kiruha [24]
The correct answer among the choices provided is option C. The magnitude of the sum of 20 and 25 might be 12. Inequality triangle equation is used to determine if 12 is right.
<span>12+20 > 25 (correct)
12+25 > 20 (correct)
20+25 > 12 (correct)</span>
6 0
3 years ago
The MRI (Magnetic Resonance Imaging) body scanners used in hospitals operate at a frequency of 400 MHz (M = 106 ). Calculate the
horrorfan [7]

Answer:

Energy, E=2.65\times 10^{-25}\ J

Explanation:

It is given that,

The MRI (Magnetic Resonance Imaging) body scanners used in hospitals operate at a frequency of 400 MHz,

\nu=400\ MHz=400\times 10^6\ Hz=4\times 10^8\ Hz

We need to find the energy for a photon having this frequency. The energy of a photon is given by :

E=h\nu

E=6.63\times 10^{-34}\ J-s\times 4\times 10^8\ Hz

E=2.65\times 10^{-25}\ J

So, the energy of the photon is 2.65\times 10^{-25}\ J. Hence, this is the required solution.

6 0
3 years ago
As a solid element melts, the atoms become __________ and they have __________ attraction for one another. more separated, more
galina1969 [7]
The complete statement is 

As a solid element melts, the atoms become more separated and they have less attraction for one another. 

Let me explain to you how this happens. In solid phase. Its molecules are arranged in a very compact manner that is why it takes a definite shape and volume. When it is heated, the kinetic energy of the molecules increases. This is characterized by more frequent collisions. The rise in temperature causes the molecules to move rapidly by vibrating. When it reaches an amount of energy that causes the solid to change phase, this is called the latent energy. The molecules break their form and move farther away from each other until it resembles that of a liquid melting. At this point, the molecules would have lesser attraction because of the distance between them.
8 0
3 years ago
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