if an electromagnet is used to pick up nails and other metal objects, what happens when the current is turned off?

100.0 J of work accelerates a 0.500 kg hockey puck across an ice rink (a frictionless

Olegator [25]

Answer:

d. 100.0 J

Explanation:

To solve this problem we must use the theorem of work and energy conservation. This tells us that the mechanical energy in the final state is equal to the mechanical energy in the initial state plus the work done on a body. In this way we come to the following equation:

E₁ + W₁₋₂ = E₂

where:

E₁ = mechanical energy at state 1. [J] (units of Joules)

E₂ = mechanical energy at state 2. [J]

W₁₋₂ = work done from 1 to 2 [J]

We have to remember that mechanical energy is defined as the sum of potential energy plus kinetic energy.

The energy in the initial state is zero, since there is no movement of the hockey puck before imparting force. E₁ = 0.

The Work on the hockey puck is equal to:

W₁₋₂ = 100 [J]

100 = E₂

Since the ice rink is horizontal there is no potential energy, there is only kinetic energy

Ek = 100 [J]

It can be said that the work applied on the hockey puck turns into kinetic energy

6 0

3 years ago

A fruit bat falls from the roof of a cave. We know that her potential energy was

bulgar [2K]

Answer:

v = 15.65 m/s

Explanation:

We use conservation of mechanical energy between initial (i) and final (f) states:

Pi + KEi = Pf + KEf

At the top of the cave at the instant the bat starts to fall, there is only potential energy since the bat's velocity is zero.

Pi = m g h = 600 J

and the KEi = 0 J (no velocity)

Knowing the height of the cave's roof (12.8 m) , we can find the mass of the bat:

m = 600 J / (g 12.5) = 4.9 kg

Using conservation of mechanical energy, the final state is:

Pf + KEf = 600 J

with Pf = 0 (just touching the ground)

KEf= 1/2 4.9 (v^2)

and we solve for the velocity:

600 J = 0 + 1/2 4.9 (v^2)

v^2 = 600 * 2 / 4.9 = 244.9

v = 15.65 m/s

5 0

3 years ago

In order for work to be done a___ must be exerted on an object causing it to___

Fed [463]

In order for work to be done a force must be exerted on an object causing it to move

8 0

2 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 678 m 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,

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