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11111nata11111 [884]
3 years ago
15

"A boat that can travel at 4.0 km/h in still water crosses a river with a current of 2.0 km/h. At what angle must the boat be po

inted upstream (that is, relative to its actual path) to go straight across the river?

Physics
1 answer:
IRISSAK [1]3 years ago
8 0

Answer:

30 degrees

Explanation:

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How much work is done if you push a 200 N box across a floor with a force of 50 N for a distance of 20m
vovikov84 [41]
<h2>Answer: 1000 J</h2>

The Work W done by a Force F refers to the release of potential energy from a body that is moved by the application of that force to overcome a resistance along a path.  

It should be noted that it is a scalar magnitude, and its unit in the International System of Units is the Joule (like energy). Therefore, 1 Joule is the work done by a force of 1 Newton when moving an object, in the direction of the force, along 1 meter:  

1J=(1N)(1m)=Nm  

Now, when the applied force is constant and the direction of the force and the direction of the movement are parallel, the equation to calculate it is:  

W=(F)(d) (1)

When they are not parallel, both directions form an angle, let's call it \alpha. In that case the expression to calculate the Work is:  

W=Fdcos{\alpha} (2)

For example, in order to push the 200 N box across the floor, you have to apply a force along the distance d to overcome the resistance of the weight of the box (its 200 N).  

In this case both <u>(the force and the distance in the path) are parallel</u>, so the work W performed is the product of the force exerted to push the box F=50N by the distance traveled d. as shown in equation (1).

Hence:

W=(50N)(20m)  

W=1000Nm=1000J >>>>This is the work  

8 0
3 years ago
A radio wave transmits 38.5 W/m2 of power per unit area. A flat surface of area A is perpendicular to the direction of propagati
Margaret [11]

Answer:

P=2.57\times 10^{-7}\ N/m^2

Explanation:

Given that,

A radio wave transmits 38.5 W/m² of power per unit area.

A flat surface of area A is perpendicular to the direction of propagation of the wave.

We need to find the radiation pressure on it. It is given by the formula as follows :

P=\dfrac{2I}{c}

Where

c is speed of light

Putting all the values, we get :

P=\dfrac{2\times 38.5}{3\times 10^8}\\\\=2.57\times 10^{-7}\ N/m^2

So, the radiation pressure is 2.57\times 10^{-7}\ N/m^2.

3 0
3 years ago
A proton, moving north, enters a magnetic field. Because of this field, the proton curves downward. We may conclude that the mag
PIT_PIT [208]

Answer:

towards the west

4 0
3 years ago
You are bungee jumping from a bridge. Initially, while you are falling the slack bungee cord isn’t exerting any forces or torque
harina [27]

Answer:

he fall movement we see that both the force is different from zero, and the torque is different from zero.

When analyzing the statements the d is true

Explanation:

Let's pose the solution of this problem, to be able to analyze the firm affirmations.

When the person is falling, the weight acts on them all the time, initially the rope has no force, but at the moment it begins to lash it exerts a force towards the top that is proportional to the lengthening of the rope.

The equation for this part is

                 Fe - W = m a  

                 k x - mg = m a

As the axis of rotation is located at the top where they jump, there is a torque.

What is it

                Fe y - W y = I α

angular and linear acceleration are related

       a = α r

       Fe y - W y = I a / r

In the fall movement we see that both the force is different from zero, and the torque is different from zero.

When analyzing the statements the d is true

4 0
3 years ago
When you stretch a spring 13 cm past its natural length, it exerts a force of 21
zloy xaker [14]

Answer:

A. 1.6 N/cm

Explanation:

spring constant = 21/13 = 1.6 N/cm

8 0
3 years ago
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