A nut threaded on a bolt, fixed to a bicycle frame, is tightened by means of a spanner. The perpendicular distance between the axis of the nut and the line of action of the force [tex]\( F \)[/tex] applied to the free end of the spanner is 0.15 m. [tex]\( F \)[/tex] is also perpendicular to the axis of the nut.

What magnitude of [tex]\( F \)[/tex] produces a couple of 10.5 Nm about the axis?



Answer :

To solve for the force [tex]\( F \)[/tex] that produces a torque (or moment) of 10.5 Nm (Newton-meters) using a spanner, we need to understand the relationship between force, torque, and distance.

### Step-by-Step Solution

1. Identify the known values:
- The perpendicular distance [tex]\( d \)[/tex] between the axis of the nut and the line of action of the force applied is [tex]\( 0.15 \)[/tex] meters.
- The torque [tex]\( \tau \)[/tex] generated by the force is [tex]\( 10.5 \)[/tex] Nm.

2. Understand the relationship between force, torque, and distance:
- Torque ([tex]\( \tau \)[/tex]) is given by the product of the force ([tex]\( F \)[/tex]) and the perpendicular distance ([tex]\( d \)[/tex]):
[tex]\[ \tau = F \times d \][/tex]
- Here, the force is perpendicular to the axis, which directly applies to this formula.

3. Rearrange the formula to solve for the force [tex]\( F \)[/tex]:
- We need to isolate [tex]\( F \)[/tex] in the equation:
[tex]\[ F = \frac{\tau}{d} \][/tex]

4. Substitute the given values into the equation:
- Substitute [tex]\( \tau = 10.5 \, \text{Nm} \)[/tex] and [tex]\( d = 0.15 \, \text{m} \)[/tex]:
[tex]\[ F = \frac{10.5}{0.15} \][/tex]

5. Calculate the force [tex]\( F \)[/tex]:
- Perform the division:
[tex]\[ F = 70 \, \text{N} \][/tex]

### Conclusion

The magnitude of the force [tex]\( F \)[/tex] needed to produce a torque of 10.5 Nm using a spanner with a perpendicular distance of 0.15 meters is [tex]\(\boxed{70 \, \text{N}}\)[/tex].