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3 years ago

8

A ball is thrown horizontally at a height of 2.2 meters at a velocity of 65m/s off a cliff. Assume no air resistance. How long u

ntil the ball reaches the ground?

1 answer:

slega [8]3 years ago

8 0

The horizontal motion has no effect on the vertical drop.

From a drop, the distance the ball falls in 'T' seconds is

D = 4.9 T^2

so

2.2 = 4.9 T^2

T^2 = 2.2/4.9

T^2 = 0.449 sec^2

T = 0.67 second

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L 5.1.5 Quiz: Electromagnetic Forces

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Answer: B

According to Coulomb: Like charges repel each other; unlike charges attract. Thus, two negative or positives charges repel one another, while a positive charge attracts a negative charge.

We see that the only diagram who shows two like charges and their Electromagnetic Forces is B

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6. The electric field caused by an electron is weakest near the electron.

OLga [1]

6. "The electric field caused by an electron is weakest near the electron" is FALSE.

7. "An electric field becomes weaker as distance from the electron increase" is TRUE.

<u>Explanation:</u>

The "electrical field" covers the electrical charge and exerts, attracts or repels other charges in the field.The electric field caused by an electron is strongest near the electron while it become weak as distance from the electron increase.

The reason behind is, at a point the direction of the field line is at that point the direction of the field. The relative magnitude of the electric field will be proportional to the field line density. The field is strongest where the field lines are near together and when the field lines are at increasing distance the field is weakest.

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Light is incident on a piece of glass in air at an angle of 33 degrees from the normal. If the index of refraction of the glass

lilavasa [31]

About 21 to 22 degrees

as below

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3 years ago

How much work in joules is required to lift a 23 kg box up from the ground to your waist that is 1.0 meters high, carry it 6 met

PSYCHO15rus [73]

Answer:

2682

Explanation:

Work done is given by :

Work = Force x distance

= mg x d

So, work done in lifting the box of 23 kg up to my waist of 1 m high is :

W = mg x d

= 23 x 9.18 x 1

= 211.14

Now work done carrying the box horizontally 6 meters across the room is

W = mg x d

= 23 x 9.18 x 6

= 1266.84

Work done in placing the box on the shelf that is 5.7 m above the ground is

W = mg x d

= 23 x 9.18 x 5.7

= 1203.49

So the total work done is = 211.14 + 1266.84 + 1203.49

= 2681.47

= 2682 (rounding off)

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2 years ago

Water is being boiled in an open kettle that has a 0.52-cm-thick circular aluminum bottom with a radius of 12.0 cm. If the water

tangare [24]

Answer:

$T_b=107.3784\ ^{\circ}C$

Explanation:

Given:

thickness of the base of the kettle, $dx=0.52\ cm=5.2\times 10^{-3}\ m$

radius of the base of the kettle, $r=0.12\ m$

temperature of the top surface of the kettle base, $T_t=100^{\circ}C$

rate of heat transfer through the kettle to boil water, $\dot Q=0.409\ kg.min^{-1}$

We have the latent heat vaporization of water, $L=2260\times 10^3\ J.kg^{-1}$

and thermal conductivity of aluminium, $k=240\ W.m^{-1}.K^{-1}$

<u>So, the heat rate:</u>

$\dot Q=\frac{0.409\times 2260000}{60}$

$\dot Q=15405.67\ W$

<u>From the Fourier's law of conduction we have:</u>

$\dot Q=k.A.\frac{dT}{dx}$

$\dot Q=k\times \pi.r^2\times \frac{T_b-T_t}{5.2\times 10^{-3}}$

where:

$A=$ area of the surface through which conduction occurs

$T_b=$ temperature of the bottom surface

$15405.67=240\times \pi\times 0.12^2\times \frac{T_b-100}{5.2\times 10^{-3}}$

$T_b=107.3784\ ^{\circ}C$ is the temperature of the bottom of the base surface of the kettle.

6 0

3 years ago