2067 Q.No. 10b OR Water flows into an inverted conical
essel at the rate of 24 m³/m. When the depth of water depth
of water is 4 m, how fast is the level rising, assuming that the
eight of the vessel is 8 m and the radius at the top is 2 m? [4]



Answer :

To find how fast the water level is rising in the inverted conical vessel, we can use related rates and the concept of similar triangles. Here's a step-by-step approach to solving this problem: 1. **Identify the Given Information**: - Water flow rate = 24 m³/min - Depth of water = 4 m - Height of the vessel = 8 m - Radius at the top = 2 m 2. **Determine the Volume of the Water in the Vessel**: - The volume of a cone is V = (1/3) * π * r² * h, where r is the radius and h is the height. - Substituting the values, V = (1/3) * π * (2)² * 4 = 16π m³. 3. **Apply Related Rates**: - The rate of change of volume with respect to time is dV/dt = 24 m³/min. - We want to find the rate at which the water level is rising, dh/dt. 4. **Use Similar Triangles**: - By considering similar triangles, we can set up a proportion between the large and small cones formed by the changing water level. - The ratio of the radius of the small cone to the large cone is 2:4 or 1:2. 5. **Relate Volumes and Heights**: - Since the ratio of volumes is the cube of the ratio of heights, we have (1/8) = (1/2)³. - Now differentiate with respect to time to get (1/8) dV/dt = (1/2)³ dh/dt. 6. **Solve for dh/dt**: - Substituting dV/dt = 24 m³/min into the equation, we get (1/8) * 24 = (1/8) dh/dt. - Solving, dh/dt = 3 m/min. Therefore, the water level is rising at a rate of 3 meters per minute in the inverted conical vessel when the depth of water is 4 meters.