Physics, 28.03.2020 08:39 val6298

A girl is sitting in a sled sliding horizontally along some snow (there is friction present). The mass of the girl is 28.4 kg and the mass of the sled is 15.3 kg.

The force of friction acting on the sled as it slides is -96 N.

If the sled has an initial velocity of 41.8 m/s, and it slides for 3.76 seconds before it hits a wall.

(Ignoring the unfortunate mess with the wall) How much work did friction do during this time?

*Hint: you cannot solve the problem in 1 step with the current information, you will need to find acceleration, and use time to find something else before you can find an answer!

Answers: 3

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Answers

Answer from: evazquez

-13,594 J

Explanation:

As first thing, we find the acceleration of the system consisting of sled+girl. We do it by using Newton's Second Law of motion:

F=ma

where:

F = -96 N is the net force on the system (the force of friction)

m = 28.4 kg + 15.3 kg = 43.7 kg is the total mass of the girl and the sled

a is the acceleration

Solving for a, we find:

$a=\frac{F}{m}=\frac{-96}{43.7}=-2.2 m/s^2$

Where the negative sign means the direction of the acceleration is opposite to the direction of motion.

Now we find the displacement of the sled, using the suvat equation:

$s=ut+\frac{1}{2}at^2$

where:

u = 41.8 m/s is the initial velocity of the sled

t = 3.76 s is the time elapsed

a=-2.2 m/s^2 is the acceleration

Substituting, we find:

$s=(41.8)(3.76)+\frac{1}{2}(-2.2)(3.76)^2=141.6 m$

Finally, we find the work done by friction on the sled:

W=Fs

where:

F = -96 N is the force of friction

s = 141.6 m is the displacement of the system

Substituting:

W=(-96)(141.6)=-13,594 J

where the negative sign means the force of friction is opposite to the direction of motion.

Answer from: Quest

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia

Answer from: Quest

Answer sample (c); // would be best because the percentage of the energy in an incident wave that remains in a reflected wave from this material is the smallest;

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A girl is sitting in a sled sliding horizontally along some snow (there is friction present). The ma...