Earth attracts a person with a gravitational force of 7.0 × 102 newtons. What is the magnitude of the force with which the individual attracts Earth? .. A)3.0 × 102 newtons
B)7.0 × 102 newtons
C)8.5 × 102 newtons
D)9.8 × 102 newtons


Answer 1
Answer: B. In the system of the object and the earth, by Newton's third law, the object will exert and equal and opposite force upon the earth.
Answer 2


B.  7.0 × 102 newtons


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the absorption of carbon dioxide from plants can be analyzed via satellite. In the image below, green represents land areas where carbon dioxide is being absorbed, and blue represents sea areas where carbon dioxide is being absorbed. The darker the color, the more carbon that location absorbs each year. In this world map, land areas are colored green and ocean areas are colored blue. The greener or bluer the location, the more carbon that location absorbs each year. Location A is very green. Public Domain What can you conclude about Location A?


Since green represents land areas where carbon dioxide is being absorbed. The darker the color, the more carbon that location absorbs each year.  Since, location A is very green, it absorbs more carbon compared to other locations.

Determine the change in electric potential energy of a system of two charged objects when a -2.1-C charged object and a -5.0-C charged object move from an initial separation of 420 km to a final separation of 160 km



Change in electric potential energy ∆E = 365.72 kJ


Electric potential energy can be defined mathematically as:

E = kq1q2/r ....1

k = coulomb's constant = 9.0×10^9 N m^2/C^2

q1 = charge 1 = -2.1C

q2 = charge 2 = -5.0C

∆r = change in distance between the charges

r1 = 420km = 420000m

r2 = 160km = 160000m

From equation 1

∆E = kq1q2 (1/r2 -1/r1) ......2

Substituting the given values

∆E = 9.0×10^9 × -2.1 ×-5.0(1/160000 - 1/420000)

∆E = 94.5 × 10^9 (3.87 × 10^-6) J

∆E = 365.72 × 10^3 J

∆E = 365.72 kJ


Which material is ideal for an office door that allows light to pass through, but maintains privacy? A. clear glass

B. wood

C. frosted glass

D. metal


The answer is "C. frosted glass"


frosted glass




QUESTION 16 The cost of DVD players has dropped by $20 each year. If a DVD player cost $189 four years ago, how much does it cost today?






The present cost of DVD players has dropped by $20 each year is $109, so option A is correct.

What is cost price?

Cost price is another name for CP. Cost price is a product's initial cost. The cost is the overall expenditure needed to manufacture a good or provide a service. In order to determine profitability, the cost price is employed in the following ways:

  1. Profit is calculated in monetary terms as Selling Price (exempt from tax) minus Cost.
  2. When represented as a percentage, profit/selling price (before taxes) yields gross profit or GP %.
  3. When the goal margin is applied, the formula expense/net sales provides a percentage that equals gross profit.


The cost price of a DVD player four years ago, c = $189,

so when the cost price decreases by $20 each year then in four years it will decrease to $80

Hence, the cost of a DVD player after 4 years will be,

= 189 - 80

= $109

Therefore, the present cost of DVD players has dropped by $20 each year is $109.

To know more about cost price:


So, we have our base value for the DVD players which is $189. If it drops by $20 each year, and we want to find out how much it costs today compared to four years ago, then how will we do that? 

Well... We know that 20 times 4 is 80... So, in order to find the answer, we need to take 189 minus 40.

90 points whats the equation for how fast something will be traveling before it hits the ground. How to do the equation PLEASE EXPLAIN here is an example problem A 0.05 kg-coin is dropped from the top of a skyscraper that is 100 meters high. How fast is the coin traveling just before it hits the ground?
use GPE=M*g*h
KE= 0.5*Mass *velocity squared


given GPE=M*g*h

KE= 0.5*Mass *velocity squared

something falls n before it hits the ground,

by conservation of energy

GPE loss = KE gain

e.g. A 0.05 kg-coin is dropped from the top of a skyscraper that is 100 meters high.

so M=0.05, g=9.8m/s^2, h=100m

GPE loss=M*g*h=0.05*9.8*100


KE gain=0.5*Mass *velocity squared=GPE loss

0.5*0.05*velocity squared=49

velocity squared=49/0.5/0.05=1960


I will solve it using a different set of equations from kinematics. The same principles are the same but the equations look different. Specifically

final velocity^2 = initial velocity^2 + 2(acceleration)(displacement)

In this example, the coin has no initial velocity, acceleration is by gravity and the displacement is 100m

final velocity^2 = 0 + 2(9.8)(100)=1960

final velocity = (1960)^(1/2) = 44.3m/s


Ocean waves pass through two small openings, 20.0 m apart, in a breakwater. You're in a boat 70.0 m from the breakwater and initially midway between the openings, but the water is pretty rough. You row 33.0 m parallel to the breakwater and, for the second time, find yourself in relatively calm water. What is the wavelength of the ocean waves ?



λ = 5.65m


The Path Difference Condition is given as:

δ=  ;

where lamda is represent by the symbol (λ) and is the wavelength we are meant to calculate.

m = no of openings which is 2


n is the index of refraction of the medium in which the wave is traveling

To find δ we have;







δ=  82.15 -73.68

δ= 8.47

Again remember; to calculate the wavelength of the ocean waves; we have:


δ= 8.47

8.47 =

λ =

λ = 5.65m


How are hot spots used to track plate motion


When plates move they sometimes open small cracks that release heat from under earths plate, coming from the mantle or even the core at times, this heat allows scientists to determine where the plates are moving from and where they are moving to.


the plates from sink go to hot water then =clean



On a straight road with the +x axis chosen to point in the direction of motion, you drive for 5 hours at a constant 20 miles per hour, then in a few seconds, you speed up to 60 miles per hour and drive at this speed for 1 hour. What was the x component of average velocity for the 6-hour period, using the fundamental definition of average velocity, which is the displacement divided by the time interval?



v = 26.7 mph


During the first 5 hours, at a constant speed of 20 mph, we find the total displacement to be as follows:

Δx₁ = v₁*t₁ = 20 mph*5 h = 100 mi

Assuming we can neglect the displacement during the speeding up from 20 to 60 mph, we can find the the total displacement at 60 mph as follows:

Δx₂ = v₂*t₂ = 60 mph*1 h = 60 mi

So, the total displacement during all the trip wil be:

Δx = Δx₁ + Δx₂ = 100 mi + 60 mi = 160 mi

So we can find the the average velocity during the 6-hour period, applying the definition of average velocity, as follows:

v = Δx / Δt = 160 mi / 6 h = 26.7 mph


A parallel-plate capacitor is formed from two 2.7 cm -diameter electrodes spaced 1.4 mm apart. The electric field strength inside the capacitor is 6.0 x106 N/C



The potential difference between the plates is


Given that,

Distance = 1.4 mm

Electric field strength

Let the potential difference is V.

We need to calculate the potential difference between the plates

Using formula of electric field

Where, V = potential

d = distance

Put the value into the formula

Hence, The potential difference between the plates is

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