In an accident, a car falls into a valley and reach to the ground in 0.5 s (given `g = 9.8 m//s^2`). Find the average speed during the 0.5 s.

Options

A. 2.45 m/s
B. 1.25 m/s
C. 2.8 m/s
D. Can't determined

Explanation

To solve the problem of finding the average speed of a car that falls into a valley and reaches the ground in 0.5 seconds, we can follow these steps:

### Step-by-Step Solution:

1. **Identify Given Values:**
- Time (t) = 0.5 seconds
- Acceleration due to gravity (g) = 9.8 m/s²
- Initial velocity (u) = 0 m/s (the car starts from rest)

2. **Calculate Final Velocity (v):**
We can use the first equation of motion:
\[ v = u + gt \]
Substituting the known values:
\[ v = 0 + (9.8 \, \text{m/s}^2 \times 0.5 \, \text{s}) = 4.9 \, \text{m/s} \]

3. **Calculate Average Speed:**
The average speed (v_avg) during the time interval can be calculated using the formula:
\[ v_{avg} = \frac{u + v}{2} \]
Substituting the values of u and v:
\[ v_{avg} = \frac{0 + 4.9}{2} = \frac{4.9}{2} = 2.45 \, \text{m/s} \]

4. **Final Result:**
The average speed of the car during the 0.5 seconds is:
\[ \text{Average Speed} = 2.45 \, \text{m/s} \]