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3 years ago

Hold a pencil in front of your eye at a position where its blunt end just blocks out the Moon.

Physics

1 answer:

Valentin [98]3 years ago

4 0

Answer:

$D = 3.55 \times 10^6 m$

Explanation:

Light rays coming from moon is blocked by the pencil

so as per figure we know that angle subtended by pencil and angle subtended by moon must be same

so we have

$Angle = \frac{Arc}{Radius}$

so we have

$\frac{D}{3.8 \times 10^8 m} = \frac{0.7 cm}{75 cm}$

so we have

$D = 3.55 \times 10^6 m$

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Explain why pulleys are in the lever family.

Aleks04 [339]

Answer:

The leverage or mechanical advantage of pulleys is less obvious, but you can "gang" multiple pulleys together into two sets (blocks) and run the ropes back and forth between the two sets to increase the number of lengths of rope running between them. One end of the rope is connected (fixed) to one of the blocks, and you get to pull on the other end after it is passed back and forth between the blocks of pulleys. This is sometimes called a block and tackle arrangement. With a hook on each side of the block set, you can move a heavy load much like levers do, by multiplying the force. You have to pull more rope just like you have to move a lever more on one side of the fulcrum as compared to the other. When you get all the rope pulled out that you can, you can not move the load anymore because you have become "two-blocked" which means the two blocks are together. Credits to: Moin Khan

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3 years ago

Explain how waves, energy, and matter are related

Stels [109]

Answer:

Mechanical waves need matter to transfer energy while electromagnetic waves do not. ... Waves change direction when they move from one material into another (matter) through the process of refraction. The wave will change direction when the speed of the wave changes.

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3 years ago

Models of four atoms are shown as figures A, B, C, and D. Which two atoms represent isotopes of the same element?

timurjin [86]

C and d have the same amount of protons and electrons

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3 years ago

A 975-kg sports car (including driver) crosses the rounded top of a hill at determine (a) the normal force exerted by the road o

iVinArrow [24]

There are missing data in the text of the problem (found them on internet):
- speed of the car at the top of the hill: $v=15 m/s$
- radius of the hill: $r=100 m$

Solution:

(a) The car is moving by circular motion. There are two forces acting on the car: the weight of the car $W=mg$ (downwards) and the normal force N exerted by the road (upwards). The resultant of these two forces is equal to the centripetal force, $m \frac{v^2}{r}$ , so we can write:
$mg-N=m \frac{v^2}{r}$ (1)
By rearranging the equation and substituting the numbers, we find N:
$N=mg-m \frac{v^2}{r}=(975 kg)(9.81 m/s^2)-(975 kg) \frac{(15 m/s)^2}{100 m}=7371 N$

(b) The problem is exactly identical to step (a), but this time we have to use the mass of the driver instead of the mass of the car. Therefore, we find:
$N=mg-m \frac{v^2}{r}=(62 kg)(9.81 m/s^2)-(62 kg) \frac{(15 m/s)^2}{100 m}=469 N$

(c) To find the car speed at which the normal force is zero, we can just require N=0 in eq.(1). and the equation becomes:
$mg=m \frac{v^2}{r}$
from which we find
$v= \sqrt{gr}= \sqrt{(9.81 m/s^2)(100 m)}=31.3 m/s$

7 0

3 years ago

Define s.i unit of force explanation

kvv77 [185]

<h3><u>Answer</u> :</h3>

◈ As per newton's second law of motion, Force is defined as the product of mass and acceleration $.$

Mathematically,

$\dag\:\boxed{\bf{\purple{F=ma}}}$

Unit of mass : kg

Unit of acceleration : m/s²

Therefore,

Unit of force ➠ <u>kg m/s²</u>

SI unit : <u>N (newton)</u> or <u>kg m/s²</u>

3 0

3 years ago