A man running on A horizontal road at 8km/hr finds the rain falling ve...
Given information:
A man is running on a horizontal road at a speed of 8 km/hr. Initially, he observes the rain falling vertically. When he increases his speed to 12 km/hr, he observes that the raindrops make an angle of 30 degrees with the vertical.
To find:
The speed and direction of rain with respect to the road.
Approach:
To find the speed and direction of rain with respect to the road, we need to consider the relative motion of the man and the rain.
1. Initial observation:
- When the man is running at a speed of 8 km/hr, he observes the rain falling vertically.
- This means that the man and the raindrops are moving in the same direction with the same speed.
- So, the speed of raindrops with respect to the man is 0 km/hr.
2. Observation at increased speed:
- When the man increases his speed to 12 km/hr, he observes the raindrops making an angle of 30 degrees with the vertical.
- This means that the man and the raindrops are no longer moving in the same direction with the same speed.
- The raindrops appear to be coming at an angle to the vertical, indicating that there is a relative motion between the man and the raindrops.
- We need to find the speed and direction of this relative motion.
3. Using trigonometry:
- Let's assume the speed of rain with respect to the road is 'v' km/hr. This is the quantity we need to find.
- The speed of the man with respect to the road is given as 8 km/hr.
- We can use the concept of trigonometry to relate the speeds of the man, rain, and the relative speed.
- In a right-angled triangle formed by the vertical direction, the direction of rain, and the relative direction, we can use the sine function to relate the angles and speeds.
- We have sin(30 degrees) = (v - 8) / 12, as the component of rain's speed perpendicular to the road is (v - 8).
- Solving this equation, we can find the value of 'v'.
Calculation:
sin(30 degrees) = (v - 8) / 12
1/2 = (v - 8) / 12
12/2 = v - 8
6 + 8 = v
v = 14 km/hr
Answer:
The speed of rain with respect to the road is 14 km/hr. The rain is coming from a direction inclined at an angle of 30 degrees to the vertical.
A man running on A horizontal road at 8km/hr finds the rain falling ve...
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