In which of these samples do the molecules mist likely have the least kinetic energy

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

viktelen [127]

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.

6 0

3 years ago

The electric force between two charges A. increases with distance between the charges B. increases if either one of charges gets

beks73 [17]

Answer:

Option (A) , (b) and (d) are correct option

Explanation:

According to Coulomb's law electric force between two charges is given by

$F=\frac{1}{4\pi \epsilon _0}\frac{q_1q_2}{r^2}$

From the relation we can say that force is directly proportional to magnitude of charges and inversely proportional to distance between them '

So if we increase the distance then force will decrease

Increase if any of the charge get larger

If force is attractive then both the charge will be of different sign and is force is repulsive then both the charges of same sign

From above conclusion we can say that (a), (b) and (d) are correct option

6 0

3 years ago

A tennis player's racket applies an average force of 200. newtons to a tennis ball for 0.025 second. The average force exerted o

Sever21 [200]

Answer:

200N

Explanation:

6 0

3 years ago

The density of a block of wood is 694 kg/m3. Its mass is 689 g. We tie the block to the bottom of a swimming pool using a single

Serhud [2]

Answer:

<em>The tension in the string = 2.065 N</em>

Explanation:

From Archimedes principle,

R.d = density of the wood block/density of water = weight of the wood block/Upthrust of the wood block in water.

R.d = D₁/D₂ = W/U

W/U =D₁/D₂.................................. Equation 1

Where W = weight of the wood block, U = upthrust of the wood block in water, D₁ = Density of the wood block, D₂ = Density of water.

Making U the subject of the equation,

U = WD₂/D₁........................... Equation 2

Given: W = mg = (689/1000)9.8 = 6.75 N, D₁ = 694 kg/m³, D₂ = 1000 kg/m³.

Substituting these values into equation 2,

U = 6.75(694)/1000

U = 4684.5/1000

U = 4.685 N.

Note: Three forces act on the wood block in the pool. and they are

(i) The weight(W) acting downs

(ii) The upthrust (U) acting upwards,

(iii) The Tension (T) in the string, acting upwards.

Thus,

W = U+T

T = W - U ................................. Equation 3

Where W = 6.75 N, U = 4.685 N

T = 6.75 - 4.685

T = 2.065 N.

T = 2.065 N

<em>Thus the tension in the string = 2.065 N</em>

7 0

3 years ago

Provided the amplitude is sufficiently great, the human ear can respond to longitudinal waves over a range of frequencies from a

riadik2000 [5.3K]

Answer:

Check the explanation

Explanation:

The beat frequency is

df = f2 - f1

the wavelength is

lamda1 = (v/f1)

and lamda2 = (v/f2)

where v = 340 m/s,f1 = 25.0 kHz and f2 = 20.0 kHz

8 0

3 years ago