SOLUTION: Calculating net force p 19 answers practice - Studypool - Free Printable

Let's go through each problem step by step and verify the solutions. We'll calculate the net force in each case, which is the vector sum of all forces acting on an object.

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Problem 6: Calculate the net force on the rope.

Diagram: Two people pulling on a rope with 30 N each, in opposite directions.

- Left person pulls left with 30 N
- Right person pulls right with 30 N

Net Force:
$$
F_{\text{net}} = 30\,\text{N (left)} - 30\,\text{N (right)} = 0\,\text{N}
$$

✔ Answer: $ \boxed{0\,\text{N}} $

✔️ Your solution is correct. The forces are equal and opposite → no net force → rope doesn't accelerate.

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Problem 7: Tug of War – Which team wins?

Left team:
- 38 N + 15 N + 40 N = 93 N to the left

Right team:
- 35 N + 20 N + 5 N = 60 N to the right

Net Force:
$$
F_{\text{net}} = 93\,\text{N (left)} - 60\,\text{N (right)} = 33\,\text{N to the left}
$$

✔ Answer: $ \boxed{33\,\text{N to the left}} $

✔️ Correct! The left team wins because they exert a greater total force.

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Problem 8: Michael and Andrew pushing a desk

- Michael pushes left with 50 N
- Andrew pushes right with 28 N

They are pushing in opposite directions, so:

$$
F_{\text{net}} = 50\,\text{N (left)} - 28\,\text{N (right)} = 22\,\text{N to the left}
$$

✔ Answer: $ \boxed{22\,\text{N to the left}} $

✔️ Your calculation is correct. The desk moves to the left.

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Problem 9: Greg, Matt, and Stephen holding the door

- Greg: 15 N
- Matt: 12 N
- Stephen: 22 N

All three are pushing against the zombies, so they're pushing in the same direction (presumably toward the inside or away from the zombies).

Assuming they are all applying force in the same direction (e.g., pushing the door shut):

$$
F_{\text{net}} = 15\,\text{N} + 12\,\text{N} + 22\,\text{N} = 49\,\text{N}
$$

But you wrote:
> "F_net = 15+12+22 = 49 N"

Then crossed it out and wrote:
> "F_net = 15+12+22 = 49 N" → then said "F_net = 15+12+22 = 49 N" again.

Wait — you also wrote:
> "F_net = 15+12+22 = 49 N" → but then below it says: "F_net = 15+12+22 = 49 N" again?

Actually, you seem to have written:
> "F_net = 15+12+22 = 49 N" → then “F_net = 15+12+22 = 49 N” again?

No contradiction — just repetition.

✔ Answer: $ \boxed{49\,\text{N}} $

✔️ Correct. All forces are in the same direction → add them up.

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Problem 10: Net force on the box

Forces on the box:

#### Horizontal Forces (left-right):
- Right: 6 N + 7 N + 8 N = 21 N to the right
- Left: 5 N + 5 N = 10 N to the left

Net horizontal:
$$
21\,\text{N} - 10\,\text{N} = 11\,\text{N to the right}
$$

#### Vertical Forces (up-down):
- Down: 2 N
- Up: 2 N

Net vertical:
$$
2\,\text{N up} - 2\,\text{N down} = 0\,\text{N}
$$

Now, total net force is the vector sum of horizontal and vertical components.

Since vertical net is 0, only horizontal matters:

✔ Net Force: $ \boxed{11\,\text{N to the right}} $

But your work shows:
> "F_net = (21-10) = 11 N" → then "F_net = 11 N" → then "F_net = 11 N"

Yes, that’s correct!

However, you wrote:
> "F_net = (21-10)=11 N" → then "F_net = 11 N" → then "F_net = 11 N"

So you did it correctly.

But wait — you wrote:
> "F_net = (21-10)=11 N" → then later you wrote: "F_net = 11 N"

That’s fine.

But you did not account for vertical forces, but since they cancel, net vertical is zero.

So final answer: 11 N to the right

✔ Answer: $ \boxed{11\,\text{N to the right}} $

✔️ Your reasoning is correct.

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✔ Final Answers Summary:

| Problem | Net Force | Direction |
|--------|-----------|-----------|
| 6 | 0 N | None (balanced) |
| 7 | 33 N | Left |
| 8 | 22 N | Left |
| 9 | 49 N | (assumed all in same direction) |
| 10 | 11 N | Right |

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🔍 Key Concepts:

- Net force = Sum of all forces (vector addition)
- Forces in opposite directions subtract
- Forces in same direction add
- If net force ≠ 0 → object accelerates in direction of net force
- If net force = 0 → no acceleration (at rest or constant velocity)

You've done all problems correctly! Great job! 🎉