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Airida [17]
3 years ago
9

A boat travels upstream for 12 miles in 3 hours and returns in 2 hours traveling downstream in a river. What is the rate of the

boat in still water and the rate of the current?
Physics
1 answer:
kaheart [24]3 years ago
7 0

Answer:

Rate of boat in still water = 5mile/hour

Rate of the current= 1 mile/hr

Explanation:

The boat is moving upstream at the rate= 12miles/3hours= 4mph

The boat is moving downstream at the rate = 12miles/2hours = 6mph

Let y be the speed of boat

And C the current of water

Y + C = 6 ...eq1

Y - C = 4 ...eq2

Adding eq1 and eq2

2Y = 10

Y= 10/2 = 5

Y= 5mph

Put Y = 5 in eq2

5 + C = 6

C = 6 - 5

C= 1 mph

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I attach a 4.1 kg block to a spring that obeys Hooke's law and supply 3.8 J of energy to stretch the spring. I release the block
borishaifa [10]

Answer:

The amplitude of the oscillation is 2.82 cm

Explanation:

Given;

mass of attached block, m = 4.1 kg

energy of the stretched spring, E = 3.8 J

period of oscillation, T = 0.13 s

First, determine the spring constant, k;

T = 2\pi \sqrt{\frac{m}{k} }

where;

T is the period oscillation

m is mass of the spring

k is the spring constant

T = 2\pi \sqrt{\frac{m}{k} } \\\\k = \frac{m*4\pi ^2}{T^2} \\\\k = \frac{4.1*4*(3.142^2)}{(0.13^2)} \\\\k = 9580.088 \ N/m\\\\

Now, determine the amplitude of oscillation, A;

E = \frac{1}{2} kA^2

where;

E is the energy of the spring

k is the spring constant

A is the amplitude of the oscillation

E = \frac{1}{2} kA^2\\\\2E = kA^2\\\\A^2 = \frac{2E}{k} \\\\A = \sqrt{\frac{2E}{k} } \\\\A =  \sqrt{\frac{2*3.8}{9580.088} }\\\\A = 0.0282 \ m\\\\A = 2.82 \ cm

Therefore, the amplitude of the oscillation is 2.82 cm

8 0
3 years ago
Use the velocity vs time graph to analyze the motion of the object.
arsen [322]

Explanation:

the object has constant velocity for 2 seconds and it get a constant accelration (2ms-2)

7 0
3 years ago
What is the intensity in W/m2 of a laser beam used to burn away cancerous tissue that, when 85.0% absorbed, puts 470 J of energy
Advocard [28]

Answer:

26036485.6433 W/m²

Explanation:

E= Energy = 470 J

t = Time = 4 seconds

d = Diameter = 2.6 mm

Power is given by

P=\dfrac{E}{t}

Intensity is given by

I=\dfrac{P}{\pi r^2}\\\Rightarrow 0.85I=\dfrac{E}{t\dfrac{\pi}{4} d^2}\\\Rightarrow I=\dfrac{470}{0.85\times 4\times \dfrac{\pi}{4}\times (2.6\times 10^{-3})^2}\\\Rightarrow I=26036485.6433\ W/m^2

The intensity of the laser beam is 26036485.6433 W/m²

8 0
4 years ago
Which of the following is not a vector quantity?
maksim [4K]

Answer:

A. Speed

Explanation:

A vector quantity is a quantity which has both magnitude and direction. Here in the given options, speed is a scalar quantity but not the vector quantity.

7 0
3 years ago
In Paragraph 3 of this passage, what clues help you know the meaning of the word
n200080 [17]
The answer is d because you have to make sure that everything is right
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4 years ago
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