Question 309 of 949
A car accelerates uniformly from rest and reaches a speed of 20 m/s in 5 seconds. What is the distance covered by the car during this time?
- 50 meters
- 100 meters
- 25 meters
- 75 meters
Correct Answer:
A
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: Use the Formula for Distance
When an object accelerates uniformly, the distance (\(s\)) covered can be calculated using the formula:
\[
s = ut + \frac{1}{2} a t^2
\]
where:
- \(s\) = distance covered
- \(u\) = initial velocity
- \(a\) = acceleration
- \(t\) = time
### Step 3: Calculate the Acceleration
First, we need to find the acceleration (\(a\)). We can use the formula:
\[
a = \frac{v - u}{t}
\]
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 4: Substitute Values into the Distance Formula
Now that we have the acceleration, we can substitute \(u\), \(a\), and \(t\) into the distance formula:
\[
s = (0 \, \text{m/s})(5 \, \text{s}) + \frac{1}{2} (4 \, \text{m/s}^2)(5 \, \text{s})^2
\]
Calculating each term:
- The first term is \(0\).
- The second term is:
\[
\frac{1}{2} \times 4 \, \text{m/s}^2 \times 25 \, \text{s}^2 = 2 \times 25 = 50 \, \text{m}
\]
### Final Calculation
Thus, the total distance covered by the car is:
\[
s = 0 + 50 \, \text{m} = 50 \, \text{m}
\]
### Conclusion
The correct answer is **A. 50 meters**.
### Explanation of Other Options
- **B. 100 meters**: This option is incorrect because it suggests that the car traveled twice the actual distance calculated. This could arise from misunderstanding the relationship between speed, time, and distance.
- **C. 25 meters**: This option is incorrect as it underestimates the distance. It may result from incorrectly applying the formula or miscalculating the acceleration.
- **D. 75 meters**: This option is also incorrect. It may stem from a miscalculation in the distance formula or misunderstanding the uniform acceleration concept.
### Revision Summary
- Use the equations of motion for uniformly accelerated motion.
- Remember that the initial velocity for a car starting from rest is 0 m/s.
- Calculate acceleration using \(a = \frac{v - u}{t}\).
- Substitute values into the distance formula \(s = ut + \frac{1}{2} a t^2\) to find the distance covered.