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Kobotan [32]
3 years ago
7

A child pulls a sled up a snow-covered hill. The child does 504 J of work on the sled. If the child walks 15 m

Physics
1 answer:
Juliette [100K]3 years ago
7 0

Answer: F = 33.6 N

Explanation: work = force · distance or W = F·s

Force F = W/s = 504 J/15 m

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1. A student lifts a box of books that weighs 185 N. The box is
aksik [14]

1)  148 J

When lifting an object, the work done on the object is equal to its change in gravitational potential energy. Mathematically:

W = \Delta U = (mg) \Delta h

where

mg is the weight of the object

\Delta h is the change in height

For the box in this problem,

mg = 185 N

\Delta h = 0.800 m

Substituting into the equation, we find:

W=(185)(0.800)=148 J

2) (a) 28875 J

The work done by a force applied parallel to the direction of motion of the object is given by

W=Fd

where

F is the magnitude of the force

d is the displacement

In this problem,

F = 825 N is the force applied by the two students together

d = 35 m is the displacement of the car

Substituting,

W=(825)(35)=28875 J

2) (b) 57750 J

As seen previously, the equation that gives the work done by the force is

W=Fd

We see that the work done is proportional to the magnitude of the force: therefore, if the force is doubled, then the work done is also doubled.

The work done previously was

W = 28875 J

Now the force is doubled, so the new work done will be

W' = 2(28875)=57750 J

3) 4.4 J

In this case, the force acting on the ball is the force of gravity, whose magnitude is:

F = mg

where

m = 0.180 kg is the mass of the ball

g=9.8 m/s^2 is the acceleration of gravity

Solving the equation,

F=(0.180)(9.8)=1.76 N

Now we find the work done by gravity using the same formula applied before:

W=Fd

where d = 2.5 m is the displacement of the ball. We can apply this version of the formula since the force is parallel to the displacement. Substituting,

W=(1.76)(2.5)=4.4 J

4) 595.2 kg

In this case, we have the work done on the box:

W = 7.0 kJ = 7000 J

And we also know the change in height of the box:

\Delta h = 1.2 m

As we stated in part a), the work done on the box is equal to its change in gravitational potential energy:

W=mg \Delta h

Solving for m, we find

m=\frac{W}{g \Delta h}

And substituting the numerical values, we find the mass of the box:

m=\frac{7000}{(9.8)(1.2)}=595.2 kg

5) They do the same work

In fact, the net work done by each person on the box is equal to the change in gravitational potential energy of the box:

W=mg \Delta h

Where \Delta h is the difference in height between the final position and the initial position of the box.

This means that the work done on the box depends only on its initial and final position, not on the path taken. The two men carry the box along different paths, however the reach at the end the same position, and they started from the same position: this means that the value of \Delta h is the same for both of them, so the work they have done is exactly the same.

5 0
3 years ago
A book sits on a bookshelf without moving until a student picks it up. Which law best explains why the book remains at rest unti
svetoff [14.1K]

Answer:

Newtons first law

Explanation:

object in rest stays at rest

object in motion stays in motion

8 0
3 years ago
Why do cells have receptors? Receptors make mRNA. Receptors let the cell know when to let things in and out of the cell. Recepto
Pavlova-9 [17]

Answer: Cells have receptors because Receptors let the cell know when to let things in and out of the cell.

Explanation:

Cell receptors also called transmembrane receptors are proteins located on the surface of a cell (extracellularly) or inside the cell which receive signals that alters the functions of the cell. The functions of the cells which can be altered includes the alteration in gene transcription and the cell morphology.

Cell receptors are generally categorizes into the following groups:

--> Internal receptors

--> cell surface receptors

--> ion channel receptors

--> G protein coupled receptors

--> enzyme linked receptors

Interaction of cell membrane receptors with specific ligands that bonds to the receptors causes conformational changes in the receptor protein. This in turn, enzymatically activates the intracellular part of the protein or induces interactions between the receptor and the proteins in the cytoplasm that act as second messengers, thereby relaying the signal from the extracellular part of the receptor to the interior of the cell. This enables the cell to know when to let things in or out of it through the information conveyed.

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2 years ago
What is the process called when the moon begins to fade from a full moon to the new moon?
nataly862011 [7]
Waning is what it’s called
8 0
3 years ago
What is the beat frequency of two keys on a phone, one with a frequency of 210 Hz and the other one with a frequency of 280 Hz?
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The best frequency should be 70 Hz you simply find the difference between 280 Hz and 210 Hz
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