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3 years ago

A woman can read the large print in a newspaper only when it is at a distance of 55 cm or more from her eyes.

Physics

1 answer:

serious [3.7K]3 years ago

3 0

Answer:

Farsightedness (hyperopic)

2.79 D

Explanation:

When a person cannot see something which is close to their eyes this condition is known as farsightedness. She should use a convex lens to correct her eye sight.

u = Object distance = 22-2.7 = 19.3 cm

v = Image distance = -55+2.7 = -52.3 cm

f = Focal length

$\frac{1}{f}=\frac{1}{u}+\frac{1}{v}\\\Rightarrow \frac{1}{f}=\frac{1}{19.3}+\frac{1}{-52.3}\\\Rightarrow \frac{1}{f}=\frac{3300}{100939}\\\Rightarrow f=\frac{100939}{3300}=30.58\ cm$

The power of a lens is given by

$P=\frac{1}{f}\\\Rightarrow P=\frac{1}{0.358}=2.79\ D$

The power of her glasses should be 2.79 D

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. A newly discovered planet has three times the mass and five times the radius of Earth. What is the ratio of the acceleration d

NikAS [45]

Answer:

0.12

Explanation:

The acceleration due to gravity of a planet with mass M and radius R is given as:

g = (G*M) / R²

Where G is gravitational constant.

The mass of the planet M = 3 times the mass of earth = 3 * 5.972 * 10^24 kg

The radius of the planet R = 5 times the radius of earth = 5 * 6.371 * 10^6 m

Therefore:

g(planet) = (6.67 * 10^(-11) * 3 * 5.972 * 10^24) / (5 * 6.371 * 10^6)²

g(planet) = 1.18 m/s²

Therefore ratio of acceleration due to gravity on the surface of the planet, g(planet) to acceleration due to gravity on the surface of the planet, g(earth) is:

g(planet)/g(earth) = 1.18/9.8 = 0.12

3 0

3 years ago

A student at another university repeats the experiment you did in lab. Her target ball is 0.860 m above the floor when it is in

dexar [7]

Answer:

K = 0.076 J

Explanation:

The height of the target, h = 0.860 m

The mass of the steel ball, m = 0.0120 kg

Distance moved, d = 1.50 m

We need to find the kinetic energy (in joules) of the target ball just after it is struck. Let t is the time taken by the ball to reach the ground.

$h=ut+\dfrac{1}{2}at^2\\\\t=\sqrt{\dfrac{2h}{g}}$

Put all the values,

$t=\sqrt{\dfrac{2\times 0.860 }{9.8}} \\\\=0.418\ s$

The velocity of the ball is :

$v=\dfrac{1.5}{0.418}\\\\= $$3.58\ m/s$

The kinetic energy of the ball is :

$K=\dfrac{1}{2}mv^2\\\\K=\dfrac{1}{2}\times 0.0120\times 3.58^2\\\\=0.076\ J$

So, the required kinetic energy is 0.076 J.

6 0

3 years ago

Can you answer this math homework? Please!

kap26 [50]

$\large \mathfrak{Solution : }$

9. An object which is in circular motion (moving along a circle) is said to be accelerating because it changes it's direction constantly even if it is moving with a constant speed. cuz acceleration is change in either magnitude or direction of an object with respect to time.

therefore, it's still acceleration as change in direction with time.

10. Average speed of an object can be calculated by dividing the total distance covered by an object by time taken to cover that distance.

i.e

$\boxed{speed = \dfrac{distance}{time} }$

it can be re- arranged to find the distance as :

$\boxed{distance = speed \times time}$

$time = \dfrac{distance}{speed}$

11. speed = 20 m/s : conversion into km/h

distance covered : 4 km = 4000 m

$time = \dfrac{distance}{speed}$

$t = \dfrac{4000}{20}$

$t = 200 \: \: sec$

time taken = 200 seconds

12. let's use the first equation of motion to find the acceleration :

$v = u + at$

$50 = 80 + 120a$

$50 - 80 = 120a$

$a = \dfrac{ - 30}{120}$

$a = - \dfrac{1}{4} m/s {}^{2}$

$- 0.25 \: \: m/s {}^{2}$

3 0

3 years ago

WhaT HAPPENS WHEN a net force act's <br> on a moving object

Mumz [18]

Answer: the object will have an acceleration and the object's velocity will change.
Explanation: I just know

4 0

3 years ago

A resin tube and a PVC rod are both rubbed against styrofoam. Do

Ivan

The concepts of electrostatics allow us to find the result for the question about the electric forces in the two tubes is:

The tubes are attracted by having charges of different signs.

<h3>Electrostatics</h3>

Electrostatics studies the transfer of charge between bodies when they rub together, in generating the charges of the insulating bodies they are not mobile, so to transfer them from one body to another they must be in contact.

The force electric between charges is of two types:

Attractive. If the charges are of different signs.

Repulsive. If the charges are of the same sign.

The transferred charge depends on the bodies involved in the tables showns that the resin is positively charged when rubbed, the PVC acquires very little charge and polystyrene acquires a negative charge due to rubbing.

They indicate that the resin is rubbed with polystyrene, therefore the resin must acquire a positive charge and the polystyrene a negative charge.

Then the PVC is rubbed with the polystyrene, which initially we will assume neutral, the PVC does not acquire a charge and the polystyrenes acquires a negative charge, if the polystyrene is isolated from the ground, it shares this negative charge with the PVC, therefore the two materials remain with half of the negative charge.

Finally, we bring the resin, which is positively charged, closer to the PVC, which has a slight negative charge, therefore the two bodies must attract each other.

In conclusion using the concepts of electrostatics we can find the result for the question about the electric forces in the two tubes is:

The tubes are attracted by having charges of different signs.

Learn more about electrostatics here: brainly.com/question/17692887

6 0

2 years ago