A particle is thrown with velocity u making an angle θ with the vertic...
To solve this problem, we can use the equations of motion for projectile motion. Let's break down the problem step by step:
1. Find the time of flight:
The particle crosses the top of the first pole after 11 seconds and the top of the second pole after 3 seconds. The time of flight is the sum of the times taken to cross both poles, so:
Time of flight = 11 s + 3 s = 14 s
2. Find the vertical component of velocity:
The time of flight can be used to find the vertical component of velocity. We know that the total time of flight is equal to twice the time of ascent (when the particle is going up) because the time of descent is the same as the time of ascent. Therefore:
Time of ascent = Time of flight / 2 = 14 s / 2 = 7 s
Using the equation of motion for vertical motion:
Vertical displacement = u * sin(θ) * t - (1/2) * g * t^2
where u is the initial velocity, θ is the angle of projection, t is the time of ascent, and g is the acceleration due to gravity.
Since the particle just crosses the top of the poles, the vertical displacement is equal to the height of the poles, which is h. We can rearrange the equation to solve for the vertical component of velocity:
h = u * sin(θ) * t - (1/2) * g * t^2
3. Find the maximum height:
The maximum height is reached when the vertical component of velocity becomes zero. At this point, the particle starts to descend. Using the equation of motion for vertical motion:
0 = u * sin(θ) - g * t
Solving for t:
t = u * sin(θ) / g
Substituting this value of t into the equation for vertical displacement:
h = u * sin(θ) * (u * sin(θ) / g) - (1/2) * g * (u * sin(θ) / g)^2
Simplifying the equation:
h = (u^2 * sin^2(θ)) / (2g)
4. Substitute the given values:
We are now ready to substitute the given values into the equation to find the maximum height. The problem does not provide the values of u, θ, or h, so we cannot calculate the exact answer. However, we can see that the maximum height is directly proportional to the square of the initial velocity and the sine squared of the angle of projection. Therefore, the maximum height will be a multiple of u^2 and sin^2(θ).
To choose the correct option from the given choices, we can analyze the equation. The maximum height is proportional to u^2, so if we double the initial velocity, the maximum height will be four times larger. Similarly, if we halve the initial velocity, the maximum height will be one-fourth of the original. However, the maximum height is not affected by the height of the poles or the time it takes to cross them.
Based on this analysis, we can conclude that the correct option is (b) 19.6m.
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