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UNO [17]
3 years ago
7

A small rock is thrown vertically upward with a speed of 21.0 m/s from the edge of the roof of a 35.0-m-tall building. The rock

doesn't hit the building on its way back down and lands in the street below. Ignore air resistance.(a) What is the speed of the rock just before it hits the street?(b) How much time elapses from when the rock is thrown until it hits the street?
Physics
1 answer:
klasskru [66]3 years ago
6 0

Answer:

a) Vf = 33.78m/s

b) t = 5.478s

Explanation:

We can calculate final speed using:

Vf^{2}=Vo^{2}-2*g*\Delta Y

where Vo = 21m/s;  g = 10m/s2;   ΔY = -35m

Vf = 33.78m/s

Now, having final speed, we can calculate the amount of time elapsed:

Vf = Vo - g * t    where Vf = -33.78m/s;   Vo = 21m/s;   g = 10m/s2

t = 5.478s

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Explain the phenomenon of polarization when a dielectric slab is subjected to an electric<br> field?
Oxana [17]

A dielectric, insulating material, or an extremely bad conductor of electrical current. Due to the absence of loosely bound, or free, electrons that could wander through the material, unlike metals, dielectrics practically do not conduct current when exposed to an electric field. Electric polarization takes place instead.

<h3>What is an Electric field?</h3>
  • An electric field is an electrical property associated with every point in the space of any form of charge. An electric field is also described as the electric force per unit charge.
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The phenomenon of polarization when a dielectric slab is subjected to an electric field:

A dielectric, insulating material, or an extremely bad conductor of electrical current. Due to the absence of loosely bound, or free, electrons that could wander through the material, unlike metals, dielectrics practically do not conduct current when exposed to an electric field. Electric polarization takes place instead.

To learn more about the electric field, refer to:

brainly.com/question/14372859

#SPJ9

8 0
2 years ago
Calculate the missing variable....
OlgaM077 [116]

Answer:

option b

Explanation:

from the given formula, s=d/t

make t the subject of the formula we have

t=d/s

5/100

0.5

6 0
3 years ago
The cross section of a copper strip is 1.2 mmthick and 20 mm wide. There is a 25-A current through this cross section, with the
Naily [24]

To solve this problem it is necessary to use the concepts related to the Hall Effect and Drift velocity, that is, at the speed that an electron reaches due to a magnetic field.

The drift velocity is given by the equation:

V_d = \frac{I}{nAq}

Where

I = current

n = Number of free electrons

A = Cross-Section Area

q = charge of proton

Our values are given by,

I = 25 A

A= 1.2*20 *10^{-6} m^2

q= 1.6*10^{-19}C

N = 8.47*10^{19} mm^{-3}

V_d =\frac{25}{(1.2*20 *10^{-6})(1.6*10^{-19})(8.47*10^{19} )}

V_d = 7.68*10^{-5}m/s

The hall voltage is given by

V=\frac{IB}{ned}

Where

B= Magnetic field

n = number of free electrons

d = distance

e = charge of electron

Then using the formula and replacing,

V=\frac{(2.5)(25)}{(8.47*10^{28})(1.6*10^{-19})(1.2*10^{-3})}

V = 3.84*10^{-6}V

5 0
3 years ago
A 120 V potential difference is applied to a space heater that dissipates 674 W during operation. (a) What is its resistance dur
Annette [7]

Answer:

(a) 21.36 ohms

(b) 5.62 A

Explanation:

Parameters given:

Potential difference, V = 120 V

Power, P = 674 W

(a) Power is given as:

P = V²/R

Where R is resistance

=> R = V²/P

R = 120²/674

R = 14400/674

R = 21.36 ohms

(b) Power is also given as:

P = I*V

Where I = Current (time rate of flow of Electric charge)

=> I = P/V

I = 674/120

I = 5.62 A

6 0
3 years ago
Read 2 more answers
Calculate the average speed of a runner who runs to for 500 meters in 40 second
siniylev [52]

Answer:

12.5

Explanation:

5 0
2 years ago
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