Electromagnets have certain advantages over permanent magnets. One of the major advantage is, the amount of electric current can easily be controlled, in turn, magnetic field can be controlled. Out of all the options, option D would be the best answer.

In short, Your Answer would be option D) Electromagnets can easily be turned on and off.

Hope this helps!

5 0

3 years ago

A supply plane needs to drop a package of food to scientists working on a glacier in greenland. the plane flies 100 m above the

pishuonlain [190]

The package should be dropped <u>678 m</u> short of the target.

A package dropped from a plane which is moving at a speed v, has a horizontal velocity equal to the horizontal velocity of the plane. It has a parabolic trajectory, traversing a horizontal range x while it falls through a vertical height y.

The package has no initial vertical velocity, and it falls through a height y under the action of the acceleration due to gravity g.

Use the equation,

$y=\frac{1}{2} gt^2$

Write an expression for t, the time taken for the package to fall through y.

$t^2=\frac{2y}{g}$

Substitute 100 m for y and 9.81m/s² for g.

$t^2=\frac{2y}{g}\\ =\frac{2(100m)}{9.81m/s^2} \\ =20.39s^2\\ t=4.52s$

In the time t the package travels a horizontal distance x. The horizontal velocity of the package remains constant, since no force acts along the horizontal direction.

Therefore, the horizontal distance traveled by the package is given by,

$x=vt\\ =(150m/s)(4.52s)\\ =678m$

If the package is released <u>678m</u> before the target, the package would reach the scientists working in Greenland.

6 0

4 years ago

A 6 kg table has a net force of 15 N acting on it. What is the magnitude of the acceleration of the table?

beks73 [17]

Answer:

2.5m/s2

Explanation:

F=ma

a=F/m

a=15/6

a=2.5m/s2

8 0

3 years ago

A disk, with a radius of 0.25 m, is to be rotated like a merry-go-round through 800 rad, starting from rest, gaining angular spe

torisob [31]

Answer:

a) $T_{min} = 80\,s$

Explanation:

a) Let consider that disk accelerates and decelerates at constant rate. The expression for angular acceleration and deceleration are, respectively:

Acceleration

$\alpha_{1} = \frac{\omega_{max}^{2}}{2\cdot (400\,rad)}$

Deceleration

$\alpha_{2} = -\frac{\omega_{max}^{2}}{2\cdot (400\,rad)}$

Since angular acceleration and deceleration have same magnitude but opposite sign. Let is find the maximum allowed angular speed from maximum allowed centripetal acceleration:

$a_{r,max} = \omega_{max}^{2}\cdot r$