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Vladimir79 [104]
2 years ago
15

A man is pushing a box of mass m along the ground with a force F. The coefficient of kinetic friction between the box and the gr

ound is μk​. The box is accelerating, but then the person stops pushing and the box slides to a halt. The person then starts pushing on the box again with a force F, but the box doesn't budge. The maximum coefficient of static friction between the box and the ground is μs​. Identify which of the following statements is true?
a. F > μk/μs
b. μk > μs
c. μkmg < F <= μsmg
d. μsmg= F
Physics
1 answer:
notka56 [123]2 years ago
3 0

Answer: Option C.

Explanation:

When the box is moving, he pushes with a force F.

in this case, the coefficient is μk, and the box is accelerating, this means that the net force is not zero, so F is larger than the friction force.

When the box is still, the man pushes again with a force F, but now the box does not move, so there is no acceleration, which means that the net force is zero, then F is not greater than the maximum static friction force.

Now, the friction force between an object of mass M, and a surface with a coefficient of friction  μ is:  μ*m*g

where g is the gravitational acceleration.

Then, from the first part, we can conclude that:

μk*m*g < F

(the force F is larger than the kinetic friction force)

and from the second part, we know that:

F ≤  μs*m*g

(The force F is not greater than the static friction force)

If we write those two together, we have:

μk*m*g < F ≤  μs*m*g

Then the correct option is c.

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olga_2 [115]

The time taken for the athlete to finish the race is 20 s (Option A)

<h3>What is power? </h3>

Power is simply defined as the rate at which work is done. It can be expressed mathematically as

Power (P) = work (W) / time (t)

But

Work = weight × distance

Therefore,

Power = (weight × distance ) / time

<h3>How to determine the time </h3>
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Power = (weight × distance ) / time

5400 = (539 × 200) / t

5400 = 107800 / t

Cross multiply

5400 × t = 107800

Divide both side by 5400

t = 107800 / 5400

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5 0
1 year ago
A pendulum has 294 J of potential energy at the highest point of its swing. How much kinetic energy will it have at the bottom o
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Newton's law of conservation states that energy of an isolated system remains a constant. It can neither be created nor destroyed but can be transformed from one form to the other.


Implying the above law of conservation of energy in the case of pendulum we can conclude that at the bottom of the swing the entire potential energy gets converted to kinetic energy. Also the potential energy is zero at this point.


Mathematically also potential energy is represented as


Potential energy= mgh


Where m is the mass of the pendulum.


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At the bottom of the swing,the height is zero, hence the potential energy is also zero.


The kinetic energy is represented mathematically as


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At the bottom the pendulum has the maximum velocity. Hence the kinetic energy is maximum at the bottom.


Energy can neither be created e destroyed. It can only be transferred from one form to another. Implying this law and the above explainations we conclude that at the bottom of the pendulum,the potential energy=0 and the kinetic energy=294J as the entire potential energy is converted to kinetic energy at the bottom.



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3 years ago
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Georgia [21]

Answer:

F = 200 N

Explanation:

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Put all the values,

F = 20 kg × 10 m/s²

F = 200 N

So, the resultant force on the mass is 200 N.

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