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Marina CMI [18]
3 years ago
7

A brick is dropped from the top of a building through the air (friction is present) to the ground below. Part A How does the bri

ck's kinetic energy (K) just before striking the ground compare with the gravitational potential energy Ugrav at the top of the building? Set y=0 at the ground level. How does the brick's kinetic energy () just before striking the ground compare with the gravitational potential energy at the top of the building? Set at the ground level. K is equal to Ugrav. K is greater than Ugrav. K is less than Ugrav.
Physics
1 answer:
maria [59]3 years ago
8 0

Answer:kinetic energy is less than Potential Energy at bottom

Explanation:

Given

Brick is drop from top of tower

suppose brick Potential Energy at top is U=C

Kinetic Energy(K) of brick is =0 at top of building

Just before hitting its Potential Energy is converted to kinetic energy and some is lost due to the friction.

Therefore kinetic Energy is less than the potential energy

at bottom K < U

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After landing on an unexplored Klingon planet, Spock tests for the direction of the magnetic field by firing a beam of electrons
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Answer:

Magnetic field is in south west direction .

Explanation:

Let us represent various direction by  i , j, k . i representing east , j representing north and k representing vertically upward direction .

magnetic field is represented vectorially as follows

B = B₀ ( - i - j )

In the first case velocity of electron

v = v k

Force = q ( v x B )

= -e [ vk x B₀ ( - i - j ) ]

= evB₀ ( j -i )

Direction of force is north -west .

In the second case velocity of electron

v = vj

Force = -e [ vj x B₀ ( - i - j ) ]

= - evB₀ k

force is downward

In the third case, velocity of electron

v = v( -j +i )

Force = -e [ v( -j +i ) x B₀ ( - i - j ) ]

= 2 evB₀ k

Force is upward.

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3 years ago
Why do we need optics now a days?
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We need optics to help aid people who have short or long sightedness.
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7 0
3 years ago
The force that binds atoms together to form molecules is
DIA [1.3K]

Answer:

The electromagnetic force

Explanation:

There are four fundamental forces in nature:

- Gravitational force: it is the force that acts between any particles having mass. It is relevant only on very large scales (planets, stars), since it is the weakest of the 4 forces, so very large masses are needed in order to produce relevant effects.

- Electromagnetic force: it is the force that acts between particles with electric charge. It can be attractive or repulsive. It is the main force that acts between atoms and molecules.

- Strong nuclear force: it is the force that keeps the protons and the neutrons together inside the nucleus. It acts only on very short scales (only within the nucleus of the atom)

- Weak nuclear force: it is the force responsible for the radioactive decays of certain nuclei. It also acts on very short scales.

Therefore, the force that is responsible for binding atoms together to form molecules is the electromagnetic force.

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Jo wants to find out about floating and sinking. She puts a rubber duck and a bar of soap in a
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Answer:

the soap sinks because it is more dense than the duck.

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3 years ago
A small box of mass m1 is sitting on a board of mass m2 and length L. The board rests on a frictionless horizontal surface. The
Nadusha1986 [10]

Answer:

The constant force with least magnitude that must be applied to the board in order to pull the board out from under the box is \left( {{m_1} + {m_2}} \right){\mu _{\rm{s}}}

Explanation:

The Newton’s second law states that the net force on an object is the product of mass of the object and final acceleration of the object. The expression of newton’s second law is,

\sum {F = ma}

Here, is the sum of all the forces on the object, mm is mass of the object, and aa is the acceleration of the object.

The expression for static friction over a horizontal surface is,

F_{\rm{f}}} \leq {\mu _{\rm{s}}}mg

Here, {\mu _{\rm{s}}} is the coefficient of static friction, mm is mass of the object, and g is the acceleration due to gravity.

Use the expression of static friction and solve for maximum static friction for box of mass {m_1}

Substitute  for in the expression of maximum static friction {F_{\rm{f}}} = {\mu _{\rm{s}}}mg

{F_{\rm{f}}} = {\mu _{\rm{s}}}{m_1}g

Use the Newton’s second law for small box and solve for minimum acceleration aa to pull the box out.

Substitute  for , [/tex]{m_1}[/tex] for in the equation .

{F_{\rm{f}}} = {m_1}a

Substitute {\mu _{\rm{s}}}{m_1}g for {F_{\rm{f}}} in the equation {F_{\rm{f}}} = {m_1}a

{\mu _{\rm{s}}}{m_1}g = {m_1}a

Rearrange for a.

a = {\mu _{\rm{s}}}g

The minimum acceleration of the system of two masses at which box starts sliding can be calculated by equating the pseudo force on the mass with the maximum static friction force.

The pseudo force acts on in the direction opposite to the motion of the board and the static friction force on this mass acts in the direction opposite to the pseudo force. If these two forces are cancelled each other (balanced), then the box starts sliding.

Use the Newton’s second law for the system of box and the board.

Substitute for for in the equation .

{F_{\min }} = \left( {{m_1} + {m_2}} \right)a

Substitute for in the above equation .

{F_{\min }} = \left( {{m_1} + {m_2}} \right){\mu _{\rm{s}}}g

The constant force with least magnitude that must be applied to the board in order to pull the board out from under the box is \left( {{m_1} + {m_2}} \right){\mu _{\rm{s}}}g

There is no friction between the board and the surface. So, the force required to accelerate the system with the minimum acceleration to slide the box over the board is equal to total mass of the board and box multiplied by the acceleration of the system.

5 0
3 years ago
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