A car falls off a ledge and drops to the ground in 0.7 s. (let g=`10ms^(2)`) What is its speed on striking the ground?

Options

A. 7 `ms^(-1)`
B. 8 `ms^(-1)`
C. 4 `ms^(-1)`
D. 7 `ms^(-1)`

Answer

To solve the problem of finding the speed of the car when it strikes the ground after falling for 0.7 seconds, we can use the equations of motion under uniform acceleration.

### Step-by-Step Solution:

1. **Identify the Given Values**:
- Initial velocity (U) = 0 m/s (since the car starts from rest)
- Acceleration due to gravity (g) = 10 m/s²
- Time of fall (T) = 0.7 s

2. **Use the Equation of Motion**:
The formula to calculate the final velocity (V) when an object is in free fall is:
\[ V = U + g \cdot T \]
where:
- V = final velocity
- U = initial velocity
- g = acceleration due to gravity
- T = time of fall

3. **Substitute the Values into the Equation**:
\[ V = 0 + (10 \, \text{m/s}^2) \cdot (0.7 \, \text{s}) \]

4. **Calculate the Final Velocity**:
\[ V = 10 \cdot 0.7 = 7 \, \text{m/s} \]

5. **Conclusion**:
The speed of the car when it strikes the ground is **7 m/s**.