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Bond [772]
2 years ago
7

A river flows at a speed of 3 mph towards sea. A woman in a canoe can paddle through water at a speed of 7 mph. She wishes to pa

ddle for a total time of 2 hours, first upstream (away from the sea) then turning round and paddling back to her starting point. How long should she paddle upstream?
Physics
1 answer:
miss Akunina [59]2 years ago
8 0

Answer:

She can paddle 5.71 miles upstream.

Explanation:

A woman in a canoe can paddle through water at a speed of 7 mph

Speed with which women can paddle = 7 mph

A river flows at a speed of 3 mph towards sea.

Speed of river = 3 mph

She need to paddle for 2 hours.

Let the distance paddled to upstream be d.

We have

    Velocity to upstream = 7 - 3 = 4 mph

    Velocity to downstream = 7 + 3 = 10 mph  

    \texttt{Time for upstream = }\frac{d}{4}\\\\\texttt{Time for downstream = }\frac{d}{10}

We have

          \frac{d}{4}+\frac{d}{10}=2\\\\10d+4d=2\times 4\times 10\\\\14d=80\\\\d=5.71miles

She can paddle 5.71 miles upstream.

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Suppose you are talking by interplanetary telephone to your friend, who lives on the Moon. He tells you that he has just won a n
Savatey [412]

Answer:

The friend on moon will be richer.

Explanation:

We must calculate the mass of gold won by each person, to tell who is richer. For that purpose we will use the following formula:

W = mg

m = W/g

where,

m = mass of gold

W = weight of gold

g = acceleration due to gravity on that planet

<u>FOR FRIEND ON MOON</u>:

W = 1 N

g = 1.625 m/s²

Therefore,

m = (1 N)/(1.625 m/s²)

m(moon) = 0.6 kg

<u>FOR ME ON EARTH</u>:

W = 1 N

g = 9.8 m/s²

Therefore,

m = (1 N)/(9.8 m/s²)

m(earth) = 0.1 kg

Since, the mass of gold on moon is greater than the mass of moon on earth.

<u>Therefore, the friend on moon will be richer.</u>

7 0
2 years ago
Which of the following describes a physical change? A. A marshmallow burns over an open flame. B. Icicles melt from a rooftop. C
AnnZ [28]

Answer:

B

Explanation:

Icicles melt from a rooftop

5 0
2 years ago
A vertical spring of constant k = 400 N/m hangs at rest. When a 2 kg mass is attached to it, and it is released, the spring exte
Viefleur [7K]

Answer:

4.9 cm

Explanation:

From Hook's Law,

F = ke......................... Equation 1

Where F= force, e = extension, k = spring constant.

Note: the Force acting on the the spring is the weight of the mass.

W = mg.

F = mg.................... Equation 2

Where m = mass, g = acceleration due to gravity

Substitute equation 2 into equation 1

mg = ke

make e the subject of the equation

e = mg/k............... Equation 3.

Given: m = 2 kg, g = 9.8 m/s², k = 400 N/m

e = (2×9.8)/400

e = 19.6/400

e = 0.049 m

e = 4.9 cm

3 0
2 years ago
Which statement correctly compares and contrasts the information represented by the chemical formula and model of a compound?
Alina [70]
Models show how the atoms in a compound are connected.
6 0
2 years ago
Read 2 more answers
A box rests on the (horizontal) back of a truck. The coefficient of static friction between the box and the surface on which it
vredina [299]

Answer:

The distance is 11 m.

Explanation:

Given that,

Friction coefficient = 0.24

Time = 3.0 s

Initial velocity = 0

We need to calculate the acceleration

Using newton's second law

F = ma...(I)

Using formula of friction force

F= \mu m g....(II)

Put the value of F in the equation (II) from equation (I)

ma=\mu mg....(III)

a = \mu g

Put the value in the equation (III)

a=0.24\times9.8

a=2.352\ m/s^2

We need to calculate the distance,

Using equation of motion

s = ut+\dfrac{1}{2}at^2

s=0+\dfrac{1}{2}2.352\times(3.0)^2

s=10.584\ m\ approx\ 11\ m

Hence, The distance is 11 m.

3 0
2 years ago
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