Question 423 of 949
A car is navigating a circular track with a radius of 50 meters at a constant speed of 20 m/s. What is the centripetal force acting on the car if its mass is 800 kg?
- 1600 N
- 800 N
- 3200 N
- 400 N
Correct Answer:
A
Explanation
To determine the centripetal force acting on a car navigating a circular track, we can use the formula for centripetal force, which is given by:
\[
F_c = \frac{mv^2}{r}
\]
Where:
- \( F_c \) is the centripetal force,
- \( m \) is the mass of the object (in this case, the car),
- \( v \) is the speed of the object,
- \( r \) is the radius of the circular path.
### Step-by-Step Calculation
1. **Identify the given values**:
- Mass of the car, \( m = 800 \, \text{kg} \)
- Speed of the car, \( v = 20 \, \text{m/s} \)
- Radius of the circular track, \( r = 50 \, \text{m} \)
2. **Substitute the values into the formula**:
\[
F_c = \frac{800 \, \text{kg} \times (20 \, \text{m/s})^2}{50 \, \text{m}}
\]
3. **Calculate \( v^2 \)**:
\[
(20 \, \text{m/s})^2 = 400 \, \text{m}^2/\text{s}^2
\]
4. **Substitute \( v^2 \) back into the formula**:
\[
F_c = \frac{800 \, \text{kg} \times 400 \, \text{m}^2/\text{s}^2}{50 \, \text{m}}
\]
5. **Multiply the mass by \( v^2 \)**:
\[
800 \, \text{kg} \times 400 \, \text{m}^2/\text{s}^2 = 320000 \, \text{kg} \cdot \text{m}^2/\text{s}^2
\]
6. **Divide by the radius**:
\[
F_c = \frac{320000 \, \text{kg} \cdot \text{m}^2/\text{s}^2}{50 \, \text{m}} = 6400 \, \text{N}
\]
### Correct Answer
The calculated centripetal force is **6400 N**. However, since the options provided do not include this value, it seems there may have been a misunderstanding in the options or the question itself.
### Explanation of Options
- **Option A: 1600 N** - This is incorrect. It does not match our calculated value.
- **Option B: 800 N** - This is incorrect. It is significantly lower than the calculated centripetal force.
- **Option C: 3200 N** - This is incorrect. It is also lower than the calculated centripetal force.
- **Option D: 400 N** - This is incorrect. It is much lower than the calculated centripetal force.
### Common Pitfalls
- **Misunderstanding the formula**: Ensure you are using the correct formula for centripetal force.
- **Forgetting to square the speed**: A common mistake is to forget to square the speed when substituting into the formula.
- **Incorrect unit conversions**: Always check that the units are consistent (e.g., mass in kg, speed in m/s, radius in m).
### Revision Summary
- The formula for centripetal force is \( F_c = \frac{mv^2}{r} \).
- Always square the speed when calculating centripetal force.
- Ensure all units are consistent to avoid calculation errors.
- The centripetal force is necessary for an object to maintain circular motion at a constant speed.
In this case, the correct centripetal force calculated is **6400 N**, which does not match any of the provided options.