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2 years ago

7

Mrs. Miller is acting a little strange and is pushing as hard as she can against a wall. Using Newton's Laws, what could be say

about the force she is exerting?

2 answers:

deff fn [24]2 years ago

8 0

Newton’s 3rd Law of Motion

Stells [14]2 years ago

4 0

The wall is exerting the same amount of force back at her

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Pls help. This is about heat. I got the answer, just need the working

Mars2501 [29]

Answer:

See below

Explanation:

You have to heat the calorimeter to 100 C from 20 C

this will take .20 kg * 390 j /kg-C * 80 C = <u>6240 j</u>

You have to heat the mass of water to boiling point (100 C ) from 20C

this will take

.50 kg * 4182 j/kg-C * 80 = <u>167,280 j </u>

AND you have to add enough heat to boil off .03 kg of water:

.03 kg * (2260000 j/kg-C ) =<u> 67,800 j</u>

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Power = joules / sec = (6240 + 167280 + 67800) / 274.8 =<u> 878 watts </u>

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<u>Your answer may differ just a bit for slightly different or rounded values of specific heat or heat of fusion for water .....</u>

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2 years ago

Which biome's yearly rainfall mainly evaporates? A. taiga B. desert C. tropical rainforest D. temperate grassland

worty [1.4K]

The answer is B. desert. Deserts don't get much rainfall to begin with and most of it evaporates.

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3 years ago

What type of change accurs when a substance stays the same

Thepotemich [5.8K]

This would be a physical change because it can change back to its original form. This is like ripping paper. You can piece it back together and it still is paper.

The opposite of this is chemical change. Chemical change means the product has been changed completely like burning paper. The paper has now been turned to ash and it's impossible to change this back to its original form.

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3 years ago

A car travels 40 miles in 30 minutes.

lukranit [14]

Answer:

(a)Average velocity ,v =128.74 Km/hr

(b)Kinetic Energy , K=958546.875 Joule

(c)Distance, s=268.8m

(d)Acceleration, a= - 2.38 $m/s^2$

<u>Explanation</u>:

<u>Given</u>:

Distance travelled = 40 miles

Time taken = 30 minutes.

(A) The average velocity in kilometres/hour

Converting 40 miles into km ,

we know that,

1 mile = 1.60934

40 miles = 40 x 1.60934

so 40 miles = 64.3738 Km

similarly converting 30 minutes into hours

1 minute = $\frac{1}{60}hours$

30 minute = $\frac{30}{60}hours$

30 minute = $\frac{1}{2}hours$

Now

Average velocity = $\frac{Speed}{time}$

Substituting Values,

Average velocity = $\frac{64.3738}{\frac[1}{2}}$

Average velocity = $64.3738 \times 2$

Average velocity =128.74 Km/hr

(B) If the car weighs 1.5 tons, what is its If the car weighs 1.5 tons, what is its kinetic energy in joules (Note: you will need to convert your velocity to m/s)? in joules (Note: you will need to convert your velocity to m/s)?

Converting 1.5 tons into kg we get

1 ton = 1000 kg

so 1.5 ton =1500 kg

converting velocity to m/s

$128.74 \times \frac{5}{18}$

=>35.75 m/s----------------------------------------------------------(1)

kinetic energy K= $\frac{1}{2}mv^2$

Substituting the values,

K= $\frac{1}{2}1500(35.75)^2$

K= $\frac{1}{2}1500(1278.06)$

K= $\frac{1500 \times (1278.06)}{2}$

K= $\frac{1917093.75}{2}$

K=958546.875 Joule---------------------------------------------(2)

(c)When the driver applies the brake, it takes 15 seconds to stop. How far does the car travel (in meters) while stopping

Lets use Distance formula,

$S= ut+\frac{1}{2}at^2$

Substituting the known values,

$s= ut+\frac{1}{2}at^2$

$s= (37.75)(15)+\frac{1}{2}a(15)^2$

$s=566.25+\frac{1}{2}a(225)$

$s=566.25+\frac{(225a)}{2}$ -------------------------------------(3)

(D) What is the average acceleration of the car (in m/s2) during braking?

Using the formula

v=u +at

re arranging the formula we get,

$a = \frac{v - u}{t}$

Substituting the values

$a = \frac{0 - 35.75}{15}$

$a = \frac{- 35.75}{15}$

a= - 2.38 $m/s^2$ ----------------------------------------(4)

Now substituting 4 in 3 we get

$s=566.25+\frac{(225( - 2.38)}{2}$

$s=566.25+\frac{-535.5}{2}$

$s=536.25-267.75$

s=268.8m--------------------------------------------------------------(5)

4 0

3 years ago

Which of the following is a sign of a physical Change ?

guapka [62]

C.) i believe because the change in shape is changing the physical appearance

7 0

3 years ago

Read 2 more answers