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alekssr [168]
3 years ago
14

Which is the largest and most dense of the terrestrial planets? A.Mercury B.Venus C.Earth D.Mars

Physics
1 answer:
Effectus [21]3 years ago
7 0
C.Earth is the largest and most dense of the terrestrial planets

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A woman can row a boat at 5.60 km/h in still water. (a) If she is crossing a river where the current is 2.80 km/h, in what direc
katrin2010 [14]

Answer:

a) θ=210°, b) t=1.155hr, c) t=1.333hr, d) t=1.333hr, e) θ=180° (straight across), f) t=1hr.

Explanation:

So, the very first thing we nee to do when solving this problem is draw a diagram that represents it. In the attached picture I show a diagram for each part of this problem.

part a)

So, for her to move in a direction directly opposite her starting point, the x-component of her velocity must be de same as the velocity of the river in the opposite direction. We can use this fact to find the angle we need. If we analize the triangle I drew in the diagram, we can ses that:

cos \theta = \frac {V_{river}}{V_{boat}}

When solving for theta, we get that:

\theta =cos^{-1} ( \frac {V_{river}}{V_{boat}})

so now we can substitute the corresponding values:

\theta =cos^{-1} ( \frac {2.80km/hr}{5.60km/hr}})

Which yields:

\theta = 60^{o}

but we are measuring the angle relative to the line perpendicular to the river, positive if down the river. So we need to subtract the angle from 270° so we get:

θ=270°-60°=210°

part b)

for part b, we need to find what the y-component for the velocity of the boat is for an angle of 210° as shown in the problem, so we get that:

V_{y}=5.60km/hr*cos(210^{o})

V_{y}=-4.85km/hr

The woman will head in a negative 5.60km distance from one side to the other, so we get that the time it takes her to go to the other side of the river is:

t=\frac{y}{V_{y}}

t=\frac{5.60km}{4.85km/hr}=1.155hr

part c)

In order to find the time it takes her to travel 2.80km down and up the river, we need to find the velocities she will have in both directions. First, down stream:

V_{ds}=V_{river}+V{boat}

V_{ds}=2.80km/hr+5.60km/hr=8.40km/hr

and now up stream:

V_{us}=V_{boat}-V{river}

V_{us}=5.60km/hr-2.80km/hr=2.80km/hr

Once we got these two velocities we will now need to find the time to take each trip:

time down stream:

t_{ds}=\frac{x}{v_{ds}}

t_{ds}=\frac{2.80km}{8.40km/hr}=0.333hr

and the time up stream:

t_{us}=\frac{x}{v_{us}}

t_{us}=\frac{2.80km}{2,80km/hr}=1hr

so the total time will be:

t_{ds}+t_{us}=0.333hr+1hr=1.333hr

d) the time it takes the boat to go upstream and then downstream for the same distance is the same as the time we got on part c, since both times will be the same but they will come in different order, but their sum will be just the same:

t=1.333hr

e) For her to cross the river faster, she must row in a 180° direction (this is in a direction straight accross the river) that way she will use all her velocity to move across the river. (Even though she will move a certain distance horizontally and will not reach a point opposite to the starting point.)

f) In order to find the time it takes her to get to the other side, we need to divide the distance into the velocity of the boat.

t=\frac{d}{v_{boat}}

t=\frac{5.60km}{5.60km/hr}

so

t= 1hr

4 0
3 years ago
Read 2 more answers
Need amswer fast plz
FrozenT [24]

Answer:

I need this for may schooling

6 0
2 years ago
Describe what happens to the electric field lines when two objects with unlike charges are brought near each other.
harina [27]
Hello.

The answer is:

It creates a spark.

Then thespark can sometimes start a fire or other serious problems.

Have a nice day
4 0
3 years ago
Read 2 more answers
1. Which of the following statements best describes matter?
Rashid [163]

Answer:

Matter is anything that has mass

Explanation:

The word "matter" refers to anything that has mass, either organic or inorganic. Matter is made up of atoms, which consists of a nucleus (made up of protons, positively charged, and neutrons, electrically neutron) and electrons which revolve around the nucleus.

The number of protons in the atom determine the element: there are more than 100 different elements in nature, with different properties depending on the number of electrons they have.

Matter can be in three different states also:

- solid: the atoms are tightly bond to each other, so they cannot move

- liquids: atoms are not bond to each other, so they can slide past each other, but still they have some intermolecular forces that keep them close to each other

- gas: atoms are free to move, as there are no forces that keep them close to each other

7 0
3 years ago
Read 2 more answers
You are doing x-ray diffraction on a crystal that has a cubic structure, using 0.340-nm x rays. Part A If the lattice spacing is
Mrac [35]

Answer:

∅ = 0.26°

Explanation:

Bragg's law states that:

n×λ = 2×d×sin(∅)

<em>where:</em>

  • <em>d is the lattice spacing.</em>
  • <em>λ is the wavelength of the rays.</em>
  • <em>n is the order of the diffracted rays, n = 1.</em>

then:

sin(∅) = λ/2×d

    ∅ = sin^-1(λ/2×d)

    ∅ = 0.26°

6 0
3 years ago
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