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3 years ago

at the extact same time, youj drop a piece of notebook paper and your science out the window. the science book hit first? why?

1 answer:

8 0

The piece of paper has less mass and will glide down the window, whereas the textbook will go straight to the ground. Since the textbook has more mass and less ways of it being able to 'glide' the textbook will hit the ground first.

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How many boron atoms are there in 5 molecules of BF3? Hint: The symbol for boron is B. Submit

Thepotemich [5.8K]

Answer:

5 atoms of Boron

Explanation:

Boron makes up approximately 15.944% of the mass and the rest of the 84.056% is Fluorine. There is 5 Atoms because Boron atomic mass is 10.811 in 1 molecule of BF3 and you wanted 5 Molecules.

8 0

3 years ago

Read 2 more answers

The rates of obesity have more than doubled for children between the ages of 6 and 11 since the middle of the twentieth century.

Illusion [34]

Answer:

True

Explanation:

Obesity is a growing concern in children as rates skyrocket to an all time high

8 0

3 years ago

Suppose the price of electricity is 12.75 cents per kWºh. What

adell [148]

Answer:

The difference between the cost of operating LED and incandescent bulb is $5.1

Explanation:

We are given the cost of electricity that is 12.75 cents per kWh. We want to find out the difference in the operating cost of an incandescent and LED bulb for a time period of 2,000 hours.

Since we are not given the rating of the incandescent bulb and LED bulb, we will assume their ratings.

For a light intensity of 250 Lumens;

The average rating of an LED bulb is approximately 5 Watts.

The average rating of an incandescent bulb is approximately 25 Watts.

Now lets find out the kWh of each bulb.

Energy = Power×Time

For LED bulb:

E = 5×2,000 = 10,000 Wh

Divide by 1000 to convert into kWh

E = 10,000/1000 = 10 kWh

Cost = 12.75×10 = 127.5 cents

Cost = $1.27

For Incandescent bulb:

E = 25×2,000 = 50,000 Wh

Divide by 1000 to convert into kWh

E = 50,000/1000 = 50 kWh

Cost = 12.75×50 = 637.5 cents

Cost = $6.37

Difference in Cost:

Difference = $6.37 - $1.27 = $5.1

Therefore, the difference between the cost of operating LED and incandescent bulb is $5.1.

5 0

3 years ago

Problem 7.17 A horizontal spring with stiffness 0.8 N/m has a relaxed length of 12 cm (0.12 m). A mass of 23 grams (0.023 kg) is

Jlenok [28]

The speed of the mass v = 0.884 m/s.

<u>Explanation</u>:

Let

K1 represents the kinetic energy of the mass when it is released,

U1 represents the potential energy of the spring when the mass is released,

K2 represents the kinetic energy of the mass when the spring returns to relaxed length,

U2 represents the potential energy of the spring when the spring returns to relaxed length

The spring is stretched by 0.27 - 0.12 = 0.15 m

K1 = 0

U1 = (1/2) $\times$ 0.8 $\times$ (0.15)^2

= 0.009 J

U2 = 0

By conservation of energy,

K2 + U2 = K1 + U1

K2 + 0 = 0 + 0.009 J

K2 = 0.009 J

Let v = speed of the mass

K2 = 1/2 $\times$ m $\times$ v^2

m = 23 g = 0.023 kg

0.009 = 1/2 $\times$ 0.023 $\times$ v^2

0.009 = 0.0115 $\times$ v^2

v = √(0.009 / 0.0115)

v = 0.884 m/s.

5 0

3 years ago

An unwary football player collides with a padded goalpost while running at a velocity of 7.50 m/s and comes to a full stop after

yanalaym [24]

Answer:

a= -80.357 m/s

Explanation:

use the formula

vf^2=vi^2+2a(xf-xi)

Plug in givens

0=(7.50)^2+2a(0.350m)

solve for acceleration

a= -80.357 m/s

6 0

3 years ago