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3 years ago

10

A car speeds up as it rolls down a hill. which is this an example of? positive acceleration negative acceleration relative veloc

ity

2 answers:

alex41 [277]3 years ago

6 0

Positive acceleration

anzhelika [568]3 years ago

5 0

Positive acceleration

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How does the lever arm change if you decrease the angle of the force?

Vladimir79 [104]

Answer:

The lever arm could decrease or increase depending of the initial angle.

Explanation:

The lever arm d is calculated by:

d = rsin(θ)

where r is the radius and θ the angle between the force and the radius.

So, the increse or decrees of d depends of the sin of the angle θ, if the initial angle is greather than 90° and the angle decrease to an angle closer to 90°, the lever arm will increase but if the initial angle is 90° or lower and the angle decrease, the lever arm will decrease.

8 0

3 years ago

If this energy were used to vaporize water at 100.0 ∘C, how much water (in liters) could be vaporized? The enthalpy of vaporizat

Zanzabum

Answer:

0.429 L of water

Explanation:

First to all, you are not putting the value of the energy given to vaporize water, so, to explain better this problem, I will assume a value of energy that I took in a similar exercise before, which is 970 kJ.

Now, assuming that the water density is 1 g/mL, this is the same as saying that 1 g of water = 1 mL of water

If this is true, then, we can assume that 1 kg of water = 1 L of water.

Knowing this, we have to use the expression to get energy which is:

Q = m * ΔH

Solving for m:

m = Q / ΔH

Now "m" is the mass, but in this case, the mass of water is the same as the volume, so it's not neccesary to do a unit conversion.

Before we begin with the calculation, we need to put the enthalpy of vaporization in the correct units, which would be in grams. To do that, we need the molar mass of water:

MM = 18 g/mol

The enthalpy in mass:

ΔH = 40.7 kJ/mol / 18 g/mol = 2.261 kJ/g

Finally, solving for m:

m = 970 / 2.261 = 429 g

Converting this into volume:

429 g = 429 mL

429 / 1000 = 0.429 L of water

3 0

3 years ago

J.J. Thomson theorized that, if an atom had all of its negatively charged

Bumek [7]

Answer:

C. Positively charged

Explanation:

The plum pudding model of the atom proposes by J. J. Thomson consisted of electrons which lay embedded as the raisins within a dough or soup that was positively charged. The electron was discovered by J. J. Thomson in 1897 through cathode ray tube experiments.

Based on the plum pudding model, if all the negatively charge electrons contained in an atom are removed, the material remaining will be the <em>positively charged</em> soup

6 0

2 years ago

Calculate the kinetic energy in joules of a 1200 kg automobile moving at 18 m/s .

vodka [1.7K]

Answer:

194,400 joules of kinetic energy.

Explanation:

Remember that to calculate the Kinetic energy you need to use the next formula:

$Ke=\frac{1}{2}Mass*Velocity^2$

We know that Mass= 1200 kg and velocity is 18m/s, so we insert those values into the formula:

$Ke=\frac{1}{2}Mass*Velocity^2\\Ke=\frac{1}{2}1200kg*(18m/s)^2\\Ke=194,400 joules$

So the kinetic energy of a car moving at 18m/s with a mass of 1200 kg would be 194,400 joules.

7 0

3 years ago

Read 2 more answers

A light beam has speed c in vacuum and speed v in a certain plastic. The index of refraction n of this plastic is

Mnenie [13.5K]

Answer:

$n = \frac{c}{v}$

Explanation:

Refractive Index: It is a measure to find how fast the light travels through a medium. It is ration of the speed of light in vacuum to speed of light in the medium. Speed of light is not constant and varies depending on the density of the medium.

In vacuum the speed of light is 300000 km/s and is denoted by c. When the light beam enters any medium the speed will decrease. Here it is given that the speed in plastic is v. Thus the refractive index(n) is given as:

$n = \frac{c}{v}$

It is a dimensionless no.

3 0

3 years ago