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ollegr [7]
2 years ago
13

A man is crossing a river of width 100 m on a motorboat. The velocity of the motor boat is 4 m/s eastward and the velocity of th

e water current is 3 m/s northward.
What is the resultant velocity of the boat and how much time will it take for the man to reach the other shore of the river?

A) The resultant velocity of the motor boat is 5 m/s and it takes 20s to cross the river.

B) The resultant velocity of the motor boat is 25 m/s and it takes 5s to cross the river.

C) The resultant velocity of the motor boat is 6 m/s and it takes 20s to cross the river.

D) The resultant velocity of the motor boat is 4 m/s and it takes 33s to cross the river.
Physics
1 answer:
Airida [17]2 years ago
5 0

By the Pythagorean theorem we get 3^2+4^2=5^2. Thus the resultant velocity will be 5 m/s.

However there is a typo in the choices. It should take 25 seconds to cross the river, not 20 seconds, since the boat actually travels 125 meters due to the water current, and 125/5 = 25 seconds.

Alternatively  you can calculate the eastward component of travel and get 100 / 4 = 25 seconds.


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Consider a river flowing toward a lake at an average speed of 3 m/s at a rate of 550 m3/s at a location 58 m above the lake surf
Vladimir [108]

Answer:

1. 0.574 kJ/kg

2. 315.7 MW

Explanation:

1. The mechanical energy per unit mass of the river is given by:

E_{m} = E_{k} + E_{p}

E_{m} = \frac{1}{2}v^{2} + gh

Where:

Ek is the kinetic energy

Ep is the potential energy

v is the speed of the river = 3 m/s

g is the gravity = 9.81 m/s²

h is the height = 58 m

E_{m} = \frac{1}{2}(3 m/s)^{2} + 9.81 m/s^{2}*58 m = 0.574 kJ/Kg

Hence, the total mechanical energy of the river is 0.574 kJ/kg.

2. The power generation potential on the river is:

P = m(t)E_{m} = \rho*V(t)*E_{m} = 1000 kg/m^{3}*550 m^{3}/s*0.574 kJ/kg = 315.7 MW

Therefore, the power generation potential of the entire river is 315.7 MW.

I hope it helps you!

4 0
2 years ago
Explain and derive the equation for capillary action in the phenomenon of surface tension​
lapo4ka [179]

Answer:

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3 0
3 years ago
A boy drags a box of toys.It experiences a frictional force of 10N .calculate acceleration of the system
hodyreva [135]

Answer:

20 N

Explanation:

i believe that is right

7 0
3 years ago
The generator at a power plant produces AC at 20,000 V. A transformer steps this up to 355,000 V for transmission over power lin
Masja [62]

Answer:

Number of coil in the output is 39938

Explanation:

We have given a step up transformer

Input voltage of transformer, that is primary voltage v_p=20000volt

Output voltage, that is secondary voltage v_s=355000volt

Number of turns in primary N_p=2250

For transformer we know that \frac{V_p}{V_s}=\frac{N_p}{N_s}

\frac{20000}{355000}=\frac{2250}{N_s}

N_s=39937.5

As the number of turns can not be in fraction so number of turns in the output coil is 39938

7 0
2 years ago
Which of the following statements are true?
ale4655 [162]

Answer:

A) True. Voltmeters measure voltages

C) True. They are placed in parallel

E) True ammeters are used to measure current

Explanation:

The devices for voltage measurement are the voltmeter and ammeter

Voltmeters have very high intense resistance and are placed in parallel

The ammeters have very small resist and are placed in series

Based on this establishment, let's analyze the statements

A) True. Voltmeters measure voltages

B) False has high intense resistance

C) True. They are placed in parallel

D) False ammeters are placed in series

E) True ammeters are used to measure current

F) False ammeters have a low internal resistance

4 0
2 years ago
Read 2 more answers
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