The rider tends to fall backward when a horse start suddenly. This is due to ___________ of ______________.

Answer

To solve the question, "The rider tends to fall backward when a horse starts suddenly. This is due to ___________ of ______________," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Scenario**:
- We have a rider on a horse. Initially, both the rider and the horse are at rest, meaning they have zero velocity.

2. **Identify the Action**:
- When the horse starts moving suddenly, it accelerates forward.

3. **Apply the Concept of Inertia**:
- According to Newton's first law of motion, an object at rest will remain at rest unless acted upon by an external force. The rider, due to inertia, tends to remain in the state of rest.

4. **Analyze the Effect on the Rider**:
- As the horse moves forward, the rider's body wants to stay in its original position (at rest). This creates a relative motion where the rider appears to fall backward with respect to the horse.

5. **Conclusion**:
- Therefore, the rider tends to fall backward because of the inertia of rest.

### Final Answer:
The rider tends to fall backward when a horse starts suddenly. This is due to **inertia of rest**.

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