Question

An experiment is conducted in which a spring scale is attached to a block of iron with a weight of 82 N at rest on a sheet of aluminum. An applied force of 64 N is required to cause the block to move initially and 40 N is required to pull the block forward at a constant speed once it is in motion. Which are the coefficients of static and kinetic friction?(1 point)
Responses

0.78 and 0.49
0.78 and 0.49

2.1 and 1.3
2.1 and 1.3

1.3 and 2.1
1.3 and 2.1

0.49 and 0.78

Answer 1

To find the coefficients of static and kinetic friction, we can use the following formulas:

1. The coefficient of static friction (\( \mu_s \)) can be calculated using the formula:
\[
\mu_s = \frac{F_{s}}{N}
\]
where \( F_{s} \) is the force required to overcome static friction (initial applied force) and \( N \) is the normal force (the weight of the object).

2. The coefficient of kinetic friction (\( \mu_k \)) can be calculated using the formula:
\[
\mu_k = \frac{F_{k}}{N}
\]
where \( F_{k} \) is the force required to keep the block moving at a constant speed.

Given:
- Weight of the block, \( W = 82 \, \text{N} \) (this is the normal force, \( N \)).
- Applied force to initiate motion, \( F_{s} = 64 \, \text{N} \).
- Applied force to keep motion constant, \( F_{k} = 40 \, \text{N} \).

Now, we can calculate the coefficients of friction:

1. **Static friction:**
\[
\mu_s = \frac{F_{s}}{N} = \frac{64 \, \text{N}}{82 \, \text{N}} \approx 0.78
\]

2. **Kinetic friction:**
\[
\mu_k = \frac{F_{k}}{N} = \frac{40 \, \text{N}}{82 \, \text{N}} \approx 0.49
\]

Thus, the coefficients of static and kinetic friction are approximately \( 0.78 \) and \( 0.49 \) respectively.

The correct response is:
**0.78 and 0.49**.