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alex41 [277]
3 years ago
12

Please help!!!

Physics
1 answer:
iVinArrow [24]3 years ago
6 0

A).  Her distance traveled was (700m + 500m) = <em>1,200 meters</em>

B).  Her displacement was (700m north + 500m south) = <em>200 meters north</em>

C).  Her average speed = (distance covered) / (time to cover the distance)

Speed = (1,200 meters) / (15 seconds)

<em>Speed = 80 meters/second</em>

(Layne is an incredible walker !  That's about 179 miles per hour.)

(She walks 700m in 10 seconds.  Usain Bolt runs only 100m in 10 seconds.)

D).  Her averge velocity = (displacement) / (time)

Velocity = (200 meters north) / (15 seconds)

<em>Velocity = (13 and 1/3) m/s north</em>

(This is only about 33% faster than Usain Bolt, if he went straight instead of doubling back, and if he could keep it up for 200 meters instead of only 100 meters.)

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3 0
3 years ago
A soccer player heads the ball and sends it flying vertically upwards at a speed of 18.0 m/s . How high above the players ' head
Irina-Kira [14]

Answer:

16.53 m

Explanation:

The following data were obtained from the question:

Initial velocity (u) = 18.0 m/s.

Final velocity (v) = 0 m/s

Acceleration due to gravity (g) = 9.8 m/s²

Maximum height (h) =.?

The maximum height reached by the ball can be obtained as follow:

v² = u² – 2gh (since the ball is going against gravity)

0² = 18² – (2 × 9.8 × h)

0 = 324 – 19.6h

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19.6h = 324

Divide both side by 19.6

h = 324 / 19.6

h = 16.53 m

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6 0
3 years ago
Consider a sealed 20 cm high electronic box whose base dimensions are 40cm x 40cm placed in a vacuum chamber. The emissivity of
Genrish500 [490]

Answer:

T_{surr}=296.289\ K

In Celsius:

T_{surr}=296.289-273\\T_{surr}=23.289^oC

Explanation:

The formula we are going to use is:

\dot Q_{rad}=\epsilon\sigma A_s(T_s^4-T_{surr}^4)

Where:

ε is the emissivity

σ is the Stefan constant

T_s is the final temperature of surrounding surfaces

T_{surr} is the required temperature

A_s is the are of surrounding surface

Calculating The area:

A_s=(0.4)(0.4)+4(0.4)(0.2)\\A_s=0.48\ m^2

σ= 5.67*10^{-8}\ W/m^2.K^4

ε =0.95

T_s=55+273

T_s=328 K

\dot Q_{rad=100 W

100=0.95(5.67*10^{-8})(0.48)(328^4-T_{surr}^4)\\3867693926=(328^4-T_{surr}^4)\\T_{surr}^4=7706623130\\T_{surr}=296.289\ K

In Celsius:

T_{surr}=296.289-273\\T_{surr}=23.289^oC

8 0
3 years ago
An external resistor with resistance R is connected to a battery that has an emf E and an internal resistance r. Let P be the el
satela [25.4K]

Answer:

a) When R is very small R << r, therefore the term R+ r will equal r and the current becomes  

b) When R is very large, R >> r, therefore the term R+ r will equal R and the current becomes

Explanation:

<u>Solution  :</u>

(a) We want to get the consumed power P when R is very small. The resistor in the circuit consumed the power from this battery. In this case, the current I is leaving the source at the higher-potential terminal and the energy is being delivered to the external circuit where the rate (power) of this transfer is given by equation  in the next form  

P=∈*I-I^2*r                (1)

Where the term ∈*I is the rate at which work is done by the battery and the term I^2*r is the rate at which electrical energy is dissipated in the internal resistance of the battery. The current in the circuit depends on the internal resistance r and we can apply equation to get the current by  

I=∈/R+r                     (2)

When R is very small R << r, therefore the term R+ r will equal r and the current becomes  

I= ∈/r

Now let us plug this expression of I into equation (1) to get the consumed power  

P=∈*I-I^2*r

 =I(∈-I*r)

 =0

The consumed power when R is very small is zero  

(b) When R is very large, R >> r, therefore the term R+ r will equal R and the current becomes  

I=∈/R

The dissipated power due toll could be calculated by using equation.

P=I^2*r                (3)

Now let us plug the expression of I into equation (3) to get P  

P=I^2*R=(∈/R)^2*R

 =∈^2/R

4 0
3 years ago
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