A ball is thrown vertically upward with an initial velocity of $150 \mathrm{~m} / \mathrm{s}$. The ratio of velocity after $3 \mathrm{~s}$ and $5 \mathrm{~s}$ is $\frac{x+1}{x}$. The value of $x$ is ___________.
$\left\{\right.$ take, $\left.g=10 \mathrm{~m} / \mathrm{s}^{2}\right\}$
Solution
To solve this problem, we can use the following equation of motion for the vertical velocity at any given time $t$:
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$v = u - gt$
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Where:<br/><br/>
- $v$ is the final velocity at time $t$<br/><br/>
- $u$ is the initial velocity (150 m/s)<br/><br/>
- $g$ is the acceleration due to gravity (10 m/s²)<br/><br/>
- $t$ is the time in seconds
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First, we need to find the velocities at $t = 3 \mathrm{~s}$ and $t = 5 \mathrm{~s}$.
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For $t = 3 \mathrm{~s}$:
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$v_3 = 150 - (10)(3) = 150 - 30 = 120 \mathrm{~m} / \mathrm{s}$
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For $t = 5 \mathrm{~s}$:
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$v_5 = 150 - (10)(5) = 150 - 50 = 100 \mathrm{~m} / \mathrm{s}$
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Now we need to find the ratio of these velocities:
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$\frac{v_3}{v_5} = \frac{120}{100} = \frac{6}{5} = \frac{x + 1}{x}$
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Next, we can set up an equation to find the value of $x$:
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$\frac{6}{5} = \frac{x + 1}{x}$
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Now, we can solve for $x$:
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$6x = 5(x + 1)$<br/><br/>
$6x = 5x + 5$<br/><br/>
$x = 5$
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The value of $x$ is 5.
About this question
Subject: Physics · Chapter: Kinematics · Topic: Motion in a Straight Line
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