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Marrrta [24]
3 years ago
13

Now suppose the crate is lifted so rapidly that air resistance was significant during the raising. How much work was done by the

lifting force as the box was raised 1.5 m?
Physics
1 answer:
andrey2020 [161]3 years ago
7 0

Answer:

A

Explanation:

- The complete question is:

" A crate is lifted vertically 1.5 m and then held at rest. The crate has weight 100 N (i.e., it is  supported by an upward force of 100 N).Now suppose the crate is lifted so rapidly that air resistance was significant during the raising. How much work was done by the lifting force as the box was raised 1.5 m?"

Options:

1. More than 150 J

2. A bit less than 150 J because the air partially supported the crate.

3. No work was done.

4. Still 150 J

5. None of these

Solution:

- As the box is raised the work is done against gravity and air resistance opposes the motion of box. Hence, both the force of gravity ( Weight and air resistance act downward).

- The amount of work done is the sum of both work done against gravity and against air resistance.

-                         W = W_g + W_r

                         W > W_g

                         W > 100*1.5

                         W > 150 J

- Hence, the work done is greater than 150 J i.e work is also done against ai r resistance.  

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marysya [2.9K]

The expression of the magnetic force and solving the determinant allows to shorten the result for the value of the magnetic force are:

  • In Cartesian form  F = 2.46 i ^ - 0.605 j ^
  • In the form of magnitude and direction F = 2.53 N and θ = 346.2º

Given parameters.

  • Length of the wire on the z axis is: L = 25.0 cm = 0.25 m.
  • The current i = 9.00 A in the positive direction of the z axis.
  • The magnetic field B = (-0.242 i ^ - 0.985 j ^ -0.336 k ^ ) T

To find.

  • Magnetic force.

The magnetic force on a wire carrying a current is the vector product of the direction of the current and the magnetic field.

          F = i L x B

Where the bold letters indicate vectors, F is the force, i the current, L a vector pointing in the direction of the current and B the magnetic field.

The best way to find the force is to solve the determinant, in general, a vector (L) is written in the form of the module times a <em>unit vector</em>.

         F= i |L| \left[\begin{array}{ccc}i&j&k\\L_x&L_y&L_z\\B_x&B_y&B_z\end{array}\right]  

Let's calculate.

       F= 9.00  \ 0.25 \ \left[\begin{array}{ccc}i&j&k\\0&0&1\\-0.242&-0.985&-0.336\end{array}\right]  

       F = 2.26 \ ( - 1 B_y i  \   + 1 B_x j  \ )  

       F = 2.5 (0.985 i ^ - 0.242 j ^)

       F = ( 2.46 i ^ - 0.605 j^ ) N

To find the magnitude we use the Pythagorean theorem.

        F = \sqrt{F_x^2 + F_y^2}  

        F = \sqrt{2.46^2 + 0.605^2}  

        F = 2.53 N

Let's use trigonometry for the direction.

        Tan θ ’= \frac{F_y}{F_x}  

        θ'= tan⁻¹ \frac{F_y}{F_x}  

        θ'= tan⁻¹1 (\frac{-.605}{2.46} )

        θ’= -13.8º

To measure this angle from the positive side of the x-axis counterclockwise.

        θ = 360- θ'

        θ = 360 - 13.8

        θ = 346.2º

In conclusion using the expression of the magnetic force and solving the determinant we can shorten the result for the value of the force are:

  • In Cartesian form    F = 2.46 i ^ - 0.605 j ^
  • In the form of magnitude and direction  F = 2.53 N and θ = 346.2º

Learn more here:  brainly.com/question/2630590

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3 years ago
How many electrons should be in an atom’s valence shell (with the exception of hydrogen and helium) to become stable? 2 4 6 8.
podryga [215]

Answer:

8

Explanation:

octet rule: Atoms lose, gain, or share electrons in order to have a full valence shell of eight electrons. Hydrogen is an exception because it can hold a maximum of two electrons in its valence level.

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An electric buzzer is activated, then sealed inside a glass chamber. When all of the air is pumped out of the chamber, how is th
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The Atwood’s machine shown consists of two blocks of mass m1 and m2 that are connected by a light string that passes over a pull
Talja [164]

(A) For the system consisting of the two blocks, the change in the kinetic energy of the system is equal to work done by gravity on the system.

(D) For the system consisting of the two blocks, the pulley and the Earth, the change in the total mechanical energy of the system is zero.

<h3 /><h3>The given parameters:</h3>
  • Mass of block 1 = m1
  • Mass of block 2, = m2
  • Height of block 1 above the ground, = h1
  • Height of block 2 above the ground = h2

The total initial mechanical energy of the two block system is calculated as follows;

m_1gh_1 + \frac{1}{2} m_1v_1_i^2 = m_2gh_2 + \frac{1}{2} m_2v_2_i^2\\\\m_1gh_1 + 0 = m_2gh_2 + 0\\\\m_1gh_1 = m_2gh_2\\\\m_1gh_1 - m_2gh_2 = 0

When the block m2 reaches the ground the block m1 attains maximum height and the total mechanical energy at this point is given as;

m_1g(h_1 + h_2) + K.E_1 = \frac{1}{2}m_2v_{max}^2 + P.E_2\\\\m_1g(h_1 + h_2 ) -PE_2 = \frac{1}{2}m_2v_{max}^2 - K.E_1\\\\m_1g(h_1 + h_2 )  - 0= \frac{1}{2}m_2v_{max}^2 - 0\\\\m_1g(h_1 + h_2 )  = \frac{1}{2}m_2v_{max}^2\\\\W = \frac{1}{2}m_2v_{max}^2

Thus, we can conclude the following before the block m2 reaches the ground;

  • For the system consisting of the two blocks, the pulley and the Earth, the change in the total mechanical energy of the system is zero.
  • For the system consisting of the two blocks, the change in the kinetic energy of the system is equal to work done by gravity on the system.

Learn more about conservation of mechanical energy here: brainly.com/question/332163

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Silicon (chemical symbol Si) is located in Group 14, Period 3. Which is silicon
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