Acceleration due gravity of a body thrown up is

Options

A. `9.8ms^(-2)`
B. `-9.8ms^(-2)`
C. `+-9.8ms^(-2)`
D. zero

Answer

To determine the acceleration due to gravity of a body thrown upwards, we can analyze the situation step by step.

### Step-by-Step Solution:

1. **Understanding Acceleration due to Gravity (g)**:
- The acceleration due to gravity near the surface of the Earth is approximately \( g = 9.8 \, \text{m/s}^2 \). This value is constant and acts downward towards the center of the Earth.

2. **Direction of Motion**:
- When a body is thrown upwards, it initially moves in the upward direction. However, the acceleration due to gravity always acts downward.

3. **Sign Convention**:
- To analyze the motion, we need to establish a sign convention. If we consider the upward direction as positive, then the acceleration due to gravity, which acts downward, will be negative. Thus, we can write:
\[ g = -9.8 \, \text{m/s}^2 \]

4. **Effect of Gravity on the Thrown Body**:
- As the body moves upwards, the acceleration due to gravity opposes its motion. This means that the body will decelerate until it reaches its highest point (where its velocity becomes zero).

5. **At the Highest Point**:
- At the highest point, the upward velocity of the body will be zero, but the acceleration due to gravity is still acting downward at \( 9.8 \, \text{m/s}^2 \).

6. **Descent**:
- After reaching the highest point, the body will start descending. During the descent, the velocity of the body is in the downward direction, and the acceleration due to gravity is also in the same direction (downward). Therefore, both will be considered positive in this case.

### Final Answer:
- The magnitude of acceleration due to gravity when a body is thrown upwards is \( 9.8 \, \text{m/s}^2 \), and its direction is downward (negative if upward is considered positive).