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Bogdan [553]
3 years ago
10

A boat is headed with a velocity of 18 meters/second toward the west with respect to the water in a river. If the river is flowi

ng with a velocity of 2.5 meters/second in the same direction as the boat. What would be the magnitude of the boat’s velocity? A. 16.5 meters/second B. 20.5 meters/second C. 18 meters/second D. 2 meters/second E. 45 meters/second
Physics
1 answer:
artcher [175]3 years ago
8 0

Answer:

20.5

Explanation:

in this case, the two vectors are in the same direction, so they simply add:

total motion = 18m/s + 2.5m/s = 20.5m/s to the west

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A hot air balloon is hovering in the air when it drops a 40 Kg food package to some lost golfers. If the package is dropped from
UNO [17]
We can calculate this with the law of conservation of energy. Here we have a food package with a mass m=40 kg, that is in the height h=500 m and all of it's energy is potential. When it is dropped, it's potential energy gets converted into kinetic energy. So we can say that its kinetic and potential energy are equal, because we are neglecting air resistance:

Ek=Ep, where Ek=(1/2)*m*v² and Ep=m*g*h, where m is the mass of the body, g=9.81 m/s² and h is the height of the body.

(1/2)*m*v²=m*g*h, masses cancel out and we get:

(1/2)*v²=g*h, and we multiply by 2 both sides of the equation

v²=2*g*h, and we take the square root to get v:

v=√(2*g*h)

v=99.04 m/s

So the package is moving with the speed of v= 99.04 m/s when it hits the ground. 
5 0
3 years ago
- A fridge has a maximum static friction force
Dennis_Churaev [7]

Answer:

They will move the fridge if they all push in the same direction, but it will not move with constant velocity

Explanation:

The maximum static friction force is

F_f = -250 N (negative sign since its direction is opposite to the push applied by the people)

Sam can apply a force of 130 N, while Amir and Andre can apply a push of 65 N each, so the total force that they can apply, if they push in the same direction, will be:

F=130 + 65 +65=260 N

This force is larger than the frictional force, so the fridge will start moving.

However, the net force on the fridge will be:

\sum F = 260 N - 250 N = 10 N

And according to Newton's second law,

\sum F = ma

where m is the mass of the fridge and a its acceleration, since the net force is not zero, then the fridge will have a non-zero acceleration, so it will not move with constant  velocity.

3 0
4 years ago
To practice Problem-Solving Strategy 23.2 for continuous charge distribution problems. A straight wire of length L has a positiv
Lesechka [4]

Answer:

             E = k Q / [d(d+L)]

Explanation:

As the charge distribution is continuous we must use integrals to solve the problem, using the equation of the elective field

       E = k ∫ dq/ r² r^

"k" is the Coulomb constant 8.9875 10 9 N / m2 C2, "r" is the distance from the load to the calculation point, "dq" is the charge element  and "r^" is a unit ventor from the load element to the point.

Suppose the rod is along the x-axis, let's look for the charge density per unit length, which is constant

         λ = Q / L

If we derive from the length we have

        λ = dq/dx       ⇒    dq = L dx

We have the variation of the cgarge per unit length, now let's calculate the magnitude of the electric field produced by this small segment of charge

        dE = k dq / x²2

        dE = k λ dx / x²

Let us write the integral limits, the lower is the distance from the point to the nearest end of the rod "d" and the upper is this value plus the length of the rod "del" since with these limits we have all the chosen charge consider

        E = k \int\limits^{d+L}_d {\lambda/x^{2}} \, dx

We take out the constant magnitudes and perform the integral

        E = k λ (-1/x){(-1/x)}^{d+L} _{d}

   

Evaluating

        E = k λ [ 1/d  - 1/ (d+L)]

Using   λ = Q/L

        E = k Q/L [ 1/d  - 1/ (d+L)]

 

let's use a bit of arithmetic to simplify the expression

     [ 1/d  - 1/ (d+L)]   = L /[d(d+L)]

The final result is

     E = k Q / [d(d+L)]

3 0
3 years ago
If you slosh the water back and forth in a bathtub at the correct frequency, the water rises first at one end and then at the ot
notka56 [123]

Answer:

Velocity(v) = frequency(f) × wavelength

f = 0.3165

Wavelength = 2×length(L)

L = 157cm

Convert the length in centimetres to metre = 1.57m

v = 2×1.57 × 0.3165

v = 0.99m/s

Approx. 1m/s

Explanation:

The velocity of a wave is the product of its frequency and it's wavelength. The frequency is already known. The wavelength is the distance between two successive wave crests which is formed by sloshing water back and forth in the bath tub. Sloshing water to one end of the tub will produce a wave crest first at that end then the other completing a cycle. The wavelength will be twice the length of the bath tub as it is the distance that both crests are formed.

Wave crest is the highest point of a wave, and in this case is where the water rises to a high point in the bath tub

7 0
3 years ago
You are holding one end of an elastic cord that is fastened to a wall 3.0 m away. You begin shaking the end of the cord at 2.3 H
Karo-lina-s [1.5K]

Answer:

Time take to fill the standing wave to the entire length of the string is 1.3 sec.

Explanation:

Given :

The length of the one end x= 3m, frequency of the wave f = 2.3 Hz, wavelength of the wave λ = 1 m.

Standing wave is the example of the transverse wave, standing wave doesn't transfer energy in a medium.

We know,

∴ v = fλ

Where v = speed of the standing wave.

also, ∴ v=\frac{x}{t}

where t = time take to fill entire length of the string.

Compare above both equation,

⇒   t = \frac{3}{2.3} sec

     t = 1.3sec

Therefore, the time taken to fill entire length 0f the string is 1.3 sec.

7 0
3 years ago
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