In this case, the bags at the top of a school van are tied using a string to avoid the effect of force.

Explanation:

The bags at the top of a school van are tied using a string in order to prevent them from moving or falling due to the effect of force. Let's delve into the details to understand why force is the correct answer.

1. The Concept of Force:
Force is a fundamental concept in physics that refers to a push or pull exerted on an object. When a force is applied to an object, it causes a change in the object's state of motion. In this case, the force is exerted on the bags when the van accelerates, decelerates, or takes sharp turns.

2. Inertia:
Inertia is the tendency of an object to resist changes in its state of motion. According to Newton's first law of motion, an object at rest will remain at rest, and an object in motion will continue moving in a straight line at a constant velocity unless acted upon by an external force. In the case of the bags in the school van, their inertia would cause them to continue moving in the same direction and at the same speed as the van, which may result in them falling off or colliding with other objects.

3. Acceleration:
Acceleration is the rate at which an object's velocity changes over time. When a vehicle accelerates or decelerates, the bags at the top of the van will experience a change in their velocity. This change in velocity can cause the bags to move or fall if not properly secured.

4. Momentum:
Momentum is a property of a moving object that depends on its mass and velocity. It is defined as the product of an object's mass and velocity. While momentum is related to force, it is not the primary factor in this situation. The bags' momentum would only come into play if an external force were to act on them, such as a sudden stop or collision.

5. Effect of Force:
By tying the bags using a string, the force exerted on the bags due to the van's acceleration, deceleration, or turns is countered. The string provides a restraining force that prevents the bags from moving or falling. The tension in the string acts as an equal and opposite force to the force applied on the bags, thereby keeping them in place.

Conclusion:
In conclusion, the bags at the top of a school van are tied using a string to avoid the effect of force. The string provides a restraining force that counteracts the force exerted on the bags due to the van's acceleration, deceleration, or turns. This ensures that the bags remain in place and do not move or fall, ensuring the safety of the passengers and preventing damage to the bags or other objects.

Interia