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3 years ago

Imagine a box sitting on a shelf. What forces are acting on the box?

1 answer:

3 0

In case of an object sitting at rest on another base, there are two equal and opposite forces – Normal force and the gravity.

Answer: Option A

<u>Explanation: </u>

When an object is placed at rest position on another object, there is a force exerted by the surfaces of the two contact objects. This force is denoted as Normal Force.

When an object such as a box is placed on a shelf, its surface exerts a contact force on the base of the shelf- The Normal force directed upward. Meanwhile, the gravity stays at its action and tries to pull the box towards itself.

Both of these forces however are equal and opposite and therefore, there is zero net force on the box. That's why it remains at rest, holding on Newton's third law.

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What force is needed to accelerate 300kg rock as a rste of 4m/s

Natali [406]

Answer:

60 maybe

Explanation:

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3 years ago

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Which are characteristics of electromagnetic waves?check all that apply.

emmainna [20.7K]

Correct choices are marked in bold:

travel in straight lines and can bounce off surfaces --> TRUE, normally electromagnetic waves travel in straight lines, however they can be reflected by objects, bouncing off their surfaces

travel through space at the speed of light --> TRUE, all electromagnetic waves in space (vacuum) travel at the speed of light, $c=3\cdot 10^8 m/s$ )

travel only through matter --> FALSE; electromagnetic waves can also travel through vacuum

travel only through space --> FALSE, electromagnetic waves can also travel through matter

can bend around objects --> TRUE, this is what happens for instance when diffraction occurs: electromagnetic waves are bended around obstacles or small slits

move by particles bumping into each other --> FALSE, electromagnetic waves are oscillations of electric and magnetic fields, so no particles are involved

move by the interaction between an electric field and a magnetic field --> TRUE, electromagnetic waves consist of an electric field and a magnetic field oscillating in a direction perpendicular to the direction of motion of the wave

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3 years ago

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How would the weight of a 7-kilogram concrete block compared to the weight of a 7-kilogram metal sphere?

Hitman42 [59]

Answer:

C. The block and the sphere would have the same weight.

Explanation:

If both the block and the sphere weigh 7 kilograms then they have the same weight. They may look different, but they both weigh 7 kilograms.

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3 years ago

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An engine converts 95% of its energy to mechanical. What happens to the other 5% of its energy?

Elza [17]

Answer:

Here, 5% of energy wasted as a heat lost or work done against frictional forces.

Explanation:

No engine has yet made that can convert its all input energy into mechanical energy. Some of the input energy goes in vain in the form of heat and friction.

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3 years ago

Which letters represent constructive interference in this diffraction pattern? Check all that apply.

trasher [3.6K]

Answer: A, C and D

Explanation:

Interference occurs when two waves superimpose to form a wave having a smaller or larger amplitude.

Constructive interference is said to occur when two waves superimpose to produce a wave having larger amplitude. It occurs for the waves having phase difference of multiple of 2π. On the other hand, destructive interference occurs for the waves having phase difference π, 3π, ..and so on.

In the given picture, the bright regions represent constructive interference where as the dark ones between them represent destructive interference. Thus, the correct letters representing constructive interference are: A, C and D.

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3 years ago

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