Why would scientists use a hand lens to observe minerals?

Amy gets up from her seat on a train to move closer to the front. Just as she begins to walk forward, the train stops at a stati

Ivahew [28]

Have you ever been in a bus, a train, or a car ?
What happens to you when it stops suddenly ?

A body in motion continues in motion unless
an external force acts on it and makes it stop.

Amy's body keeps moving forward when the train stops.
She pitches forward, and if she doesn't reach out and grab
a seat or a seated person, she may lose her footing and fall
on her face.

Choice - 'A' is a very good explanation.
The other choices aren't.

'C' is a good hunch, but it only applies to her feet.
The rest of her keeps going.

'D' is nonsense. There are no mysterious forces of
'repulsion' or 'attraction' on the train.

5 0

3 years ago

Read 2 more answers

2. A uniform wire of resistance R is stretched until its length doubles. Assuming its density and resistivity remain constant, w

never [62]

Answer:

Resistance is quadrupled.

Explanation:

Solving this requires us to use the formula of resistivity.

Resistivity is usually said to be the measure of the resistance of a particular size of any given material to the electrical conduction. It is mathematically represented as

ρ = RA/L, where

ρ = the resistivity of the given material

R = the resistance of the material

A = the area of the material

L = length of the material.

From the question, we're told that the length is doubled with the resistivity and density remaining constant. If the density is constant, this makes the volume constant as well.

Volume, V = A * L. We're then told that the length is doubled. If the length is doubled, for the volume to remain constant, then the area must be halved.

Volume, V = A/2 * 2L

Making, Resistance R, subject of the formula, we have

R = ρL/A.

Since resistivity is constant and the area is halved, we then have

R = 2L / (1/2A)

R = 4L / A

If the length is doubled, we have the resistance to be quadrupled

3 0

3 years ago

Suppose a skydiver (mass =100kg) is falling towards the earth. When the skydiver is 80 m above the earth he is moving at 60 m/s

goblinko [34]

Answer:

The total mechanical energy of the skydiver is, E = 96402.6 J

Explanation:

Given data,

The mass of the skydiver, m = 100 kg

The speed of the skydiver at 80 m height, v = 60 m/s

The initial velocity of the skydiver, u = 0

Using the III equations of motion,

v² = u² + 2gs

s = v²/2g

Substituting the given values,

s = ½ 60²/ 9.8

= 18.37 m

Hence the initial total distance of the skydiver from the ground initially,

h = s + d

= 18.37 + 80

= 98.37 m

Since the total mechanical energy of a system is conserved, the total mechanical energy of the skydiver at height 'h' is equal to the total mechanical energy at height 'd'.

E = P.E + K.E

= mgh + ½ mu²

= 100 x 9.8 x 98.37 ( ∵ u = 0)

= 96402.6 J

Hence, the total mechanical energy of the skydiver is, E = 96402.6 J

5 0

3 years ago

A cylindrical bucket, open at the top, is 28.0 cm high and 11.0 cm in diameter. A circular hole with a cross-sectional area 1.55

svlad2 [7]

Answer:

so height is 0.1283 m

Explanation:

given data

height = 28 cm

diameter = 11 cm

cross-sectional area = 1.55 cm2

water flow rate = 2.46×10^−4 m3/s

to find out

How high will the water in the bucket rise

solution

we know that here

potential energy = kinetic energy

mgh = 1/2 mv²

multiply both sides by the 2 and we get

2mgh=mv²

solve it we get

√(2gh) = v ....................1

h = v²/2g ...............2

and

flow rate = A V

2.46×10^−4 = V 1.55×10^−4

V = 1.5870 m/s

so from 2

h = v²/2g

h = 1.5870²/ 2(9.81)

h = 0.1283 m

so height is 0.1283 m

6 0

4 years ago

The distance from earth to a NASA satellite traveling through the solar system is 6.0 × 109m. A command is sent to the satellite

alexandr1967 [171]

Answer:

the signal it takes 40 s to get the answer

Explanation:

As the satellite is in space the speed of radiation (waves9 is the speed of light in a vacuum, which is constant 3. 108 m / s, so we can use the uniform motion ratios to find the time.

v = d / t

t = d / v

t = 6.0 109 / 3. 108

t = 2 101 s

t = 20 s

This is the time it takes to get the signal from the earth to the satellite and it takes the same time to return, so since they send the signal it takes 40 s to get the answer

5 0

4 years ago