Question 316 of 949
A car accelerates uniformly from rest to a speed of 20 m/s in 5 seconds. What is the distance covered by the car during this time?
- 25 meters
- 50 meters
- 100 meters
- 200 meters
Correct Answer:
B
Explanation
To determine the distance covered by a car that accelerates uniformly from rest to a speed of 20 m/s in 5 seconds, we can use the equations of motion. Let's break this down step-by-step.
### Step 1: Identify the Given Information
- Initial velocity (\(u\)): 0 m/s (the car starts from rest)
- Final velocity (\(v\)): 20 m/s
- Time (\(t\)): 5 seconds
### Step 2: Calculate the Acceleration
To find the distance covered, we first need to calculate the acceleration of the car. We can use the formula for acceleration (\(a\)):
\[
a = \frac{v - u}{t}
\]
Substituting the known values:
\[
a = \frac{20 \, \text{m/s} - 0 \, \text{m/s}}{5 \, \text{s}} = \frac{20 \, \text{m/s}}{5 \, \text{s}} = 4 \, \text{m/s}^2
\]
### Step 3: Use the Distance Formula
Now that we have the acceleration, we can use the formula for distance (\(s\)) covered under uniform acceleration:
\[
s = ut + \frac{1}{2} a t^2
\]
Since the initial velocity \(u\) is 0, the formula simplifies to:
\[
s = 0 \cdot t + \frac{1}{2} a t^2 = \frac{1}{2} a t^2
\]
Substituting the values of \(a\) and \(t\):
\[
s = \frac{1}{2} \cdot 4 \, \text{m/s}^2 \cdot (5 \, \text{s})^2
\]
Calculating \(t^2\):
\[
(5 \, \text{s})^2 = 25 \, \text{s}^2
\]
Now substituting back into the distance formula:
\[
s = \frac{1}{2} \cdot 4 \, \text{m/s}^2 \cdot 25 \, \text{s}^2 = 2 \cdot 25 = 50 \, \text{m}
\]
### Conclusion
The distance covered by the car during the 5 seconds of acceleration is **50 meters**. Therefore, the correct option is **B**.
### Explanation of Other Options
- **Option A (25 meters)**: This option is incorrect because it underestimates the distance covered. It does not account for the full effect of the acceleration over the 5 seconds.
- **Option C (100 meters)**: This option is incorrect as it overestimates the distance. It may arise from a misunderstanding of the acceleration or the time involved.
- **Option D (200 meters)**: This option is also incorrect and represents a significant overestimation. It likely results from a miscalculation or misunderstanding of the uniform acceleration concept.
### Revision Summary
- Use the formula \(s = ut + \frac{1}{2} a t^2\) for distance under uniform acceleration.
- Calculate acceleration using \(a = \frac{v - u}{t}\).
- Remember that if the initial velocity is zero, the formula simplifies to \(s = \frac{1}{2} a t^2\).
- Always double-check calculations to avoid common pitfalls in physics problems.