To solve this, let's analyze the given problem step by step:

Problem Description: A bar of 5 m in length is pivoted at the extreme right. A force of 10 N is applied vertically upward at the extreme left. The problem asks for the torque (moment of force) caused.

Formula for Torque (Moment of Force):

$\tau = F \cdot r$

Where:

• $\tau$ is the torque,
• $F$ is the force applied ($10 \, \text{N}$),
• $r$ is the perpendicular distance from the pivot to the line of action of the force ($5 \, \text{m}$).

Step-by-step Calculation:

$\tau = 10 \, \text{N} \cdot 5 \, \text{m} = 50 \, \text{Nm}$

Direction of the Torque:

The force applied is vertically upward at the left end, causing a counterclockwise rotation about the pivot point. In terms of clock movement:

• Counterclockwise = "contre le sens des aiguilles d'une horloge"

Correct Answer:

The moment of force is: $\boxed{\text{c. } 50 \, \text{Nm contre le sens des aiguilles d'une montre}}$

Let me know if you'd like further details or clarification!
Here are 5 related questions for better understanding:

1. How does changing the point of application of the force affect the torque?
2. What happens to the torque if the force is applied at an angle instead of vertically?
3. How would you calculate the torque if multiple forces act on the bar?
4. What is the physical meaning of the direction of torque in real-life applications?
5. Can torque exist without a pivot point?

Tip: Always ensure the distance $r$ is perpendicular to the force applied when calculating torque!