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choli [55]
3 years ago
8

A block is given an initial velocity up an inclined plane with friction. The block comes to rest before the end of the inclined

plane.
What is the sign of the work done by gravity as the block comes to rest on the inclined plane?
Physics
1 answer:
muminat3 years ago
7 0

Answer:

The sign of the work done by gravity on a block moving up an inclined plane as the block comes to a rest on the inclined plane is **negative**.

Explanation:

Work is given mathematically as (Force).(displacement) = /F/ /d/ cos θ

where /F/ = magnitude of the force

/d/ = d = magnitude of displacement that the force moves through

θ = angle between the force and the displacement

For gravity Force,

Whenever the angle between the force and the displacement is in the range of 0° and 90°, the workdone is positive.

And whenever the angle between the force and the displacement is in the range of 90°+ to 180°. The workdone is negative.

Better explained,

For gravity, the force of gravity acts in the negative y direction, so, force of gravity is always equal to (-mg î).

If an object is falling downwards, then its displacement is in the negative y direction too; - dî.

Work done by gravity on a falling object = (-mgî).(-dî) = + mg d = mgd cos 0° = + mgd (θ = 0°) in this case

Positive work!

And for an object rising upwards, the force of gravity is still in the negative y direction too and is equal to (-mgî). But the displacement is in the positive y direction; that is, +dî

Work done by gravity on a body moving upwards = (-mgî).(dî) = - mgd = mgd cos 180° = - mgd (θ = 180°)

Negative work done!

So, for a body moving up an inclined plane, the vertical displacement is still upwards and in the positive y-direction. So, the analogy of the 2nd gravity explanation works for it.

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If an atom has 13 protons and is currently electrically neutral, what must happen to give the same atom a positive charge of +2e
Alex777 [14]

The atom must lose 2 electrons

Explanation:

An atom consists of three types of particles:

- Protons, in the nucleus, with positive electric charge +e

- Neutrons, in the nucleus, with no electric charge

- Electrons, orbiting around the nucleus, with negative electric charge -e

As a result, the net electric charge of an atom is given by the number of protons minus the number of electrons:

Q = #p - #e

For a neutral atom, the number of protons and electrons is the same, so the net charge is zero.

In order for an atom to have a positive charge of +2, it means that there must be 2 protons more than the number of electrons. Since atoms exchange electrons (and not protons), this means that the atom must have "lost" 2 electrons.

In this problem, we have an atom with 13 protons: this means that initially it also has 13 electrons. However, later the atom lost 2 electrons, and as a result, the final charge is +2e.

Learn more about atoms:

brainly.com/question/2757829

#LearnwithBrainly

5 0
3 years ago
On a highway, a car is driven 80. kilometers
nydimaria [60]

The average speed of the car for the entire trip can be calculate by using:

v=\frac{S}{t}

where S is the total distance covered by the car, and t is the total time taken.


The total distance travelled by the car is:

S=80 km+50 km+40 km=170 km

while the total time taken is:

t=1.00 h+0.50 h+0.50 h=2.00 h


so, the average speed of the car is:

v=\frac{S}{t}=\frac{170 km}{2.00 h}=85 km/h


so, the correct answer is (3) 85 km/h.

7 0
4 years ago
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Explain the process of synaptic transmission, beginning with the neurotransmitters at the axon terminal of the presynaptic cell
nydimaria [60]

The synapse is actually the link between 2 neurons. Now when an action potential contacts the synaptic knob of a neuron, the voltage-gate calcium channels are unlocked, resulting in an influx of positively charged calcium ions into the cell. This makes the vesicles containing neurotransmitters, for example acetylcholine, to travel towards the pre-synaptic membrane. When the vesicle arrives at the membrane, the contents are released into the synaptic cleft by exocytosis. Neurotransmitters disperse across the space, down to its concentration gradient, up until it reaches the post-synaptic membrane, where it connects to the correct neuroreceptors. Connecting to the neuroreceptors results in depolarisation in the post-syanaptic neuron as voltage-gated sodium channels are also opened, and the positively charged sodium ions travel into the cell. When adequate neurotransmitters bind to neuroreceptors, the post-synaptic membrane overcame the threshold level of depolarisation and an action potential is made and the impulse is transmitted.

8 0
3 years ago
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What is a neutral atom?
IgorC [24]
A neutral atom is simply an atom that has no charge.
8 0
3 years ago
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A 1.0 m string with a 5 g stopper on the end is whirled in a vertical circle. The speed of the stopper is 8 m/s at the top of th
Andrew [12]

Answer:

Explanation:

A )

At the bottom of the circle , the potential energy of the stopper is converted into kinetic energy

1/2 m V² = mg x 2r + 1/2 mv²

m is mass of stopper , V is velocity at the bottom , r is radius of the circular path which is length of the string , v is velocity at the top

1/2  V² = g x 2r + 1/2 v²

 V² = g x 4r +  v²

 V² = 9.8 x 4 +  8²

V² = 103.2

V = 10.16 m/s

B )

If T be the tension at the top

Net downward force

= mg + T . This force provides centripetal force for the circular motion

mg +T = mv² / r

T =   mv²/r -mg

= m ( v²/r - g )

= .005 ( 8²/1 -g )

= .005 x 54.2

= .27 N .

C ) At the bottom

Net force = T  - mg , T is tension at the bottom , V is velocity at bottom

T-mg = mV²/r

T = m ( V²/r +g )

= .005 ( 10.16²/1 +9.8)

= .005 x 113

= .56 N .

3 0
3 years ago
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