Home Page Textbooks Physics: Principles and Problems Page 89: Practice Problems

Physics: Principles and Problems

9th Edition

Elliott, Haase, Harper, Herzog, Margaret Zorn, Nelson, Schuler, Zitzewitz

ISBN: 9780078458132

Textbook solutions

All Solutions

Page 89: Practice Problems

Exercise 1

Solution 1

Solution 2

Step 1

1 of 2

Result

2 of 2

$$
textit{color{#c34632} $ See $ $ Answer $}
$$

Step 1

1 of 2

Since the flowerpot is falling freely, only the force of gravity is acting upon it. The net force on the flowerpot is then the force of Earth’s mass. The flowerpot represents the system. A free-body diagram looks like this:

![‘slader’](https://slader-solution-uploads.s3.amazonaws.com/dad7b544-0eae-4b67-8cda-9a41d58394de-1651407382053371.png)

Step 2

2 of 2

The force of gravity acts towards the Earth’s center, or in our case in the negative $y$-direction. A motion diagram represents the motion of an object by displaying its location at various equally spaced times on the same diagram. The motion diagram of our problem is:

![‘slader’](https://slader-solution-uploads.s3.amazonaws.com/ca20bb4c-cb00-4539-ae11-7756c80bbc52-1651407388790259.png)

Exercise 2

Step 1

1 of 2

Result

2 of 2

$$
textit{color{#c34632} $See$ $ Answer$ }
$$

Exercise 3

Step 1

1 of 2

Result

2 of 2

$$
textit{color{#c34632} $ See $ $ Answer $}
$$

Exercise 4

Step 1

1 of 2

Result

2 of 2

$$
textit{color{#c34632} $ See $ $ Explanation $}
$$

Exercise 5

Step 1

1 of 2

Result

2 of 2

$$
textit{color{#c34632} $ See $ $ Answer $}
$$

Exercise 6

Solution 1

Solution 2

Step 1

1 of 3

Known:

$$
begin{align*}
F_1&=225 mathrm{N} \
F_2&=165 mathrm{N}
end{align*}
$$

Unknown:

$$
begin{align*}
F_{net}&=?
end{align*}
$$

Step 2

2 of 3

If two forces act in the same direction, we obtain the total force by simply summing them.

$$
begin{align*}
F_{net}&=F_1+F_2 \
&=225 mathrm{N}+165 mathrm{N} \
&=390 mathrm{N}
end{align*}
$$

Result

3 of 3

$$
begin{align*}
F_{net}&=390 mathrm{N} tag{in the direction of two forces}
end{align*}
$$

Step 1

1 of 4

$mathbf{Known:}$

From the question, we know that, $F_{1}$ is 225 N and $F_{2}$ is 165 N

Step 2

2 of 4

$mathbf{Formula:}$

If both the forces are in same direction, they will be added but if their direction is opposite, they will be substracted.

In this question, both forces are in same direction.

So therefore, the formula will be:

$textcolor{#c34632}{F_{net} = F_{1} + F_{2}}$

Step 3

3 of 4

$mathbf{Working:}$

1) Using the formula stated in cell 2.

$F_{net}$ =$F_{1}$ + $F_{2}$

2) Substituting the values in the formula :

$F_{net}$ = 225 + 165

$$
boxed{ F_{net} = 390 text{ N }}
$$

Result

4 of 4

$$
boxed{ F_{net} = 390 text{ N }}
$$

Exercise 7

Step 1

1 of 2

Known:

$$
begin{align*}
F_1&=225 mathrm{N} \
F_2&=-165 mathrm{N}
end{align*}
$$

Signs indicate direction only.
Unkonown:

$$
begin{align*}
F_{net}&=?
end{align*}
$$

When two forces act in opposite directions, we also get the net force by summing but now we have to pay attention to the sign of the forces.

$$
begin{align*}
F_{net}&=F_1+F_2 \
&=225 mathrm{N}-165 mathrm{N} \
&=60 mathrm{N}
end{align*}
$$

Note that the net force is a positive sign which means it is looking in the direction of a larger force.

Result

2 of 2

$$
begin{align*}
F_{net}&=60 mathrm{N} tag{in the direction of larger force}
end{align*}
$$

Exercise 8

Step 1

1 of 2

Known:

$$
begin{align*}
F_{Alutia}&=35 mathrm{N} \
F_{Seward}&=42 mathrm{N} \
F_{Kodiak}&=-53 mathrm{N}
end{align*}
$$

For the positive direction, we chose the east direction.

Unkown:

$$
begin{align*}
F_{net}&=?
end{align*}
$$

To get net force, we add upp forces of individual dogs.

$$
begin{align*}
F_{net}&=F_{Alutia}+F_{Seward}+F_{Kodiak} \
&=35 mathrm{N}+42 mathrm{N}-53 mathrm{N} \
&=24 mathrm{N}
end{align*}
$$

The sign of the total force is positive, ie in the eastern direction.

Result

2 of 2

$F_{net}=24$ N in eastern direction.

unlock

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Page 89: Practice Problems

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