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In straight line motion if a particle is at rest at an instant then at that instant its acceration a)must be zero b) must be positive c)may be zero d) must be negative?
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In straight line motion if a particle is at rest at an instant then at...
**Introduction**

In straight line motion, the acceleration of a particle determines how its velocity changes over time. When a particle is at rest, its velocity is zero, which means there is no change in velocity. However, the acceleration of the particle can still have different values.

**Explanation**

1. **Acceleration and Velocity**
- Acceleration is the rate of change of velocity with respect to time. It is a vector quantity, meaning it has both magnitude and direction.
- Velocity, on the other hand, is the rate of change of position with respect to time. It is also a vector quantity.
- When a particle is at rest, its velocity is zero. This implies that the particle is not moving, and there is no change in position over time.

2. **Acceleration Possibilities**
a) **Acceleration must be zero**: In some cases, when a particle is at rest, its acceleration can be zero. This occurs when the particle remains stationary without any external forces acting on it. In this situation, there is no change in velocity, and hence, the acceleration is zero.
b) **Acceleration may be zero**: However, it is also possible for a particle to be at rest and still have a non-zero acceleration. This occurs when multiple forces act on the particle, but their resultant force is zero. In such cases, the individual forces cancel each other out, resulting in no net force, and therefore, no change in velocity. Though the particle is at rest, its acceleration is not zero but balanced by other forces.
c) **Acceleration must be positive or negative**: If a particle is at rest and there is an unbalanced force acting on it, then the acceleration must be either positive or negative. A positive acceleration indicates that the particle is gaining speed in the positive direction, while a negative acceleration indicates that the particle is slowing down or moving in the negative direction.

**Conclusion**

When a particle is at rest in straight line motion, its velocity is zero. The acceleration of the particle can be zero if no external forces act on it, or it can be non-zero if there is a balanced or unbalanced force acting on the particle. Therefore, the correct answer is that the acceleration may be zero (option c) or it may be positive or negative, depending on the forces involved.
Community Answer
In straight line motion if a particle is at rest at an instant then at...
May be zero ...(NOT ZERO ALWAYS.. ) ... Let's take an example: if you throw a ball in air it will reach a height them stop and fall back... Meanwhile it stopped in air there was accleration of 9.8 m/s²..! (i.e there was a non zero accleration)
... Hope you understood what I explained
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In straight line motion if a particle is at rest at an instant then at that instant its acceration a)must be zero b) must be positive c)may be zero d) must be negative?
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