Ask question

Ask question

All categories

2 years ago

6

A nearsighted person wants to see an apple that is 7 meters away but can only clearly see objects that are at most 62 cm away fr

om her eyes. Eyeglasses made of diverging corrective lenses can help her to see the apple clearly. If her glasses are 2.5 cm in front of her eyes, what should be the power of these corrective lenses to allow her to see the apple?

1 answer:

natulia [17]2 years ago

6 0

Answer:

The power of the corrective lenses is 3.162 D.

Explanation:

Given that,

Object distance = 70 cm

Image distance = 62 cm

Distance between eyes and glasses = 2.5 cm

Eyeglasses made of diverging corrective lenses can help her to see the apple clearly

So now ,

Object distance from glass =70-2.5 = 67.5 cm

Image distance from glass = 62-2.5 = 59.5 cm

We need to calculate the focal length

Using formula for focal length

$\dfrac{1}{f}=\dfrac{1}{v}+\dfrac{1}{u}$

$\dfrac{1}{f}=-\dfrac{1}{59.5}-\dfrac{1}{67.5}$

$\dfrac{1}{f}=-\dfrac{508}{16065}\ cm$

We need to calculate the power of lens

Using formula of power

$P=\dfrac{100}{f}$

$P=-\dfrac{508}{16065}\times100$

$P=-3.162 \ D$

Negative sign shows the lens is diverging.

Hence, The power of the corrective lenses is 3.162 D.

You might be interested in

A 1.50-m cylinder of radius 1.10 cm is made of a complicated mixture of materials. Its resistivity depends on the distance x fro

MArishka [77]

Answer:

Resistance = 3.35* $10^{-4}$ Ω

Explanation:

Since resistance R = ρ $\frac{L}{A}$

whereas $\rho(x) = a + bx^2$

resistivity is given for two ends. At the left end resistivity is $2.25* 10^{-8}$ whereas x at the left end will be 0 as distance is zero. Thus

$2.25*10^{-8} = a + b(0)^2\\ 2.25*10^{-8} = a + 0 \\2.25*10^{-8} = a$

At the right end x will be equal to the length of the rod, so $x = 1.50\\8.50*10^{-8} = (2.25*10^{-8}) + ( b* (1.50)^2 )\\8.50*10^{-8} - (2.25*10^{-8}) = b*2.25\\\frac{6.25*10^{-8}}{2.25} = b\\b = 2.77 *10^{-8}$

Thus resistance will be R = ρ $\frac{L}{A}$

where A = π $r^2$

so,

$R = \frac{8.50*10^{-8} * 1.50}{3.14*(1.10*10^{-2})^2} \\R=3.35 * 10 ^{-4}$

6 0

2 years ago

7. A mother pushes her 9.5 kg baby in her 5kg baby carriage over the grass with a force of 110N @ an angle

jasenka [17]

Weight of the carriage $=(m+M)g =142.1\ N$

Normal force $=Fsin(\theta) + W = 197.1\ N$

Frictional force $=\mu N=27.59\ N$

Acceleration $=4.66\ m\ s^{-2}$

Explanation:

We have to look into the FBD of the carriage.

Horizontal forces and Vertical forces separately.

To calculate Weight we know that both the mass of the baby and the carriage will be added.

So Weight(W) $=(m+M)\times g =(9.5+5)\ kg \times 9.8 =142.1\ Newton\ (N)$

To calculate normal force we have to look upon the vertical component of forces, as Normal force is acting vertically.We have weight which is a downward force along with $F_x$ , force of $110\ N$ acting vertically downward.Both are downward and Normal is upward so Normal force $=Summation\ of\ both\ forces$

Normal force (N) $= Fsin(\theta)+W=110sin(30) + 142.1 =197.1\ N$

Frictional force (f) $=\mu N=0.14\times 197.1 =27.59\ N$

To calculate acceleration we will use Newtons second law.

That is Force is product of mass and acceleration.

We can see in the diagram that $F_y=Horizontal$ and $F_x=Vertical$ component of forces.

So Fnet = Fy(Horizontal) - f(friction) $= m\times a$

Acceleration (a) = $\frac{Fcos(\theta)-\mu N}{mass(m)} =\frac{(95.26-27.59)}{14.5}= 4.66\ m\ s{^2 }$

So we have the weight of the carriage, normal force,frictional force and acceleration.

3 0

2 years ago

If Katie swims from one end of the pool, to the other side, and then swims back to her original spot, her average velocity is ha

Crank

Answer:

false.

Explanation:

Ok, we define average velocity as the sum of the initial and final velocity divided by two.

Remember that the velocity is a vector, so it has a direction.

Then when she goes from the 1st end to the other, the velocity is positive

When she goes back, the velocity is negative

if both cases the magnitude of the velocity, the speed, is the same, then the average velocity is:

AV = (V + (-V))/2 = 0

While the average speed is the quotient between the total distance traveled (twice the length of the pool) and the time it took to travel it.

So we already can see that the average velocity will not be equal to half of the average speed.

The statement is false

4 0

2 years ago

A mover uses a ramp to load a crate of nails onto a truck. The crate, which must be lifted 1.5 m from the street to the bed of t

const2013 [10]

Answer: M.A = 3

Explanation:

A ramp is an example of an inclined plain. Where the

Height H = 1.5 m

Length L = 4.5 m

Mechanical advantage of a machine is the ratio of the load to effort. While mechanical advantage M.A of an inclined plain is the ratio of the length of the plain to the height of the plain.

M.A = L/H

Substitute the values of L and H into the formula

M.A = 4.5/1.5 = 3

The mechanical advantage of the ramp is 3

8 0

2 years ago

two negative charge of -2.0 c and a positive charge of 3.0 c are separated by 80 m what is the force between two charges

kozerog [31]

The Coulomb force is equal to the constant k times the product of charge one and charge two over radius.

F=k((q1q2)/r)

6 0

2 years ago