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user100 [1]
2 years ago
15

A river has a steady speed of 0.566 m/s. A student swims upstream a distance of 1.57 km and returns (still swimming) to the star

ting point. If the student can swim at a speed of 1.17 m/s in still water, how long does the trip take? Answer in units of s. Compare this with the time the trip would take if the water were still; i.e., what is the time in the river minus the time in still water? Answer in units of s.
Physics
1 answer:
MArishka [77]2 years ago
5 0

Answer:

3503.72 seconds

819.96 seconds

Explanation:

V_r=Velocity of river = 0.566 m/s

V_s=Velocity of student = 1.17 m/s

Distance to travel = 1.57 km = 1570 m

So,

Time = Distance / Speed

\frac{1570}{V_s-V_r}+\frac{1570}{V_s+V_r}=t\\\Rightarrow t=\frac{1570}{1.17-0.566}+\frac{1570}{1.17+0.566}\\\Rightarrow t=3503.72\ s

Time taken by the student to complete the trip is 3503.72 seconds

In still water

\frac{1570}{V_s}+\frac{1570}{V_s}=t\\\Rightarrow t=\frac{1570}{1.17}+\frac{1570}{1.17}\\\Rightarrow t=2683.76\ s

The difference in time between moving water and still water is 3503.72-2683.76 = 819.96 seconds

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Jerry the mouse is running along a straight desert road at a constant velocity of 18 m/s. If a certain Tom cat wants to capture
Kruka [31]

Answer:

a) t = 1.75 s

b) x = 31.5 m

Explanation:

a) The time at which Tom should drop the net can be found using the following equation:

y_{f} = y_{0} + v_{oy}t - \frac{1}{2}gt^{2}

Where:

y_{f}: is the final height = 0

y₀: is the initial height = 15 m

g: is the gravity = 9.81 m/s²

v_{0y}: is the initial vertical velocity of the net = 0 (it is dropped from rest)

0 = 15m - \frac{1}{2}9.81 m/s^{2}*t^{2}

t = \sqrt{\frac{2*15 m}{9.81 m/s^{2}}} = 1.75 s

Hence, Tom should drop the net at 1.75 s before Jerry is under the bridge.

b) We can find the distance at which is Jerry when Tom drops the net as follows:

v = \frac{x}{t}

x = v*t = 18 m/s*1.75 m = 31.5 m

Then, Jerry is at 31.5 meters from the bridge when Jerry drops the net.

I hope it helps you!                                                                    

3 0
2 years ago
PLEASE HELP!!! URGENTTT
Ludmilka [50]

Answer:

For the first one, its "attract"

4 0
2 years ago
A _____ is used in a motor to switch the direction of the magnetic field created by the current.
insens350 [35]

Answer:

A _commutator_ is used in a motor to switch the direction of the magnetic field created by the current.

The rotating part of a motor that holds the electromagnets is called the __armature___.

Electric current passes through the _brushes_ and into the electromagnets in an electric motor.

A motor turns _electrical_ energy into _mechanical_ energy.

Explanation:

A commutator, which is a split ring rotary switching device, reverses the direction of the current between the external circuit and the rotor. Reversing the current reverses the magnetic field.

The armature comprises the rotating part of the motor and the electromagnets

A brush is the electrical contact for conducting current through the moving and stationary parts of an electric motor

An electric motor turns electrical energy into mechanical energy.

8 0
3 years ago
If you ran 15 km/h for 20 min, how much distance would you cover?
nikitadnepr [17]
Since we have 15 kilometers per hour, and we're looking for 20 minutes, let's set up proportions.
20/60 minutes = x/15
20/60 = 1/3, so let's leave that simplified.
1/3 = x/15
Look at the denominators, 3 to 15 is a factor of 5, so multiply the numerator by 5.
1 • 5 = 5, so you will cover 5 kilometers in 20 minutes.

I hope this helps!
4 0
2 years ago
The Gulf Stream off the east coast of the United States can flow at a rapid 3.9 m/s to the north. A ship in this current has a c
Alex Ar [27]

Answer:

72.54 degree west of south

Explanation:

flow = 3.9 m/s north

speed = 11 m/s

to find out

point due west from the current position

solution

we know here water is flowing north and ship must go south at an equal rate so that the velocities cancel and the ship just goes west

so it become like triangle with 3.3 point down and the hypotenuse is 11

so by triangle

hypotenuse ×cos(angle) = adjacent side

11 ×cos(angle) = 3.3

cos(angle) = 0.3

angle = 72.54 degree west of south

3 0
3 years ago
Read 2 more answers
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