Easy MCQ +4 / -1 PYQ · JEE Mains 2021

The ranges and heights for two projectiles projected with the same initial velocity at angles 42$^\circ$ and 48$^\circ$ with the horizontal are R1, R2 and H1, H2 respectively. Choose the correct option :

  1. A R<sub>1</sub> &gt; R<sub>2</sub> and H<sub>1</sub> = H<sub>2</sub>
  2. B R<sub>1</sub> = R<sub>2</sub> and H<sub>1</sub> &lt; H<sub>2</sub> Correct answer
  3. C R<sub>1</sub> &lt; R<sub>2</sub> and H<sub>1</sub> &lt; H<sub>2</sub>
  4. D R<sub>1</sub> = R<sub>2</sub> and H<sub>1</sub> = H<sub>2</sub>

Solution

Here, two projectiles are projected at angles 42$^\circ$ and 48$^\circ$ with same initial velocity.<br/><br/>As we know the expression of range of projectile, <br/><br/>Range $= {{{u^2}\sin 2\theta } \over g}$<br/><br/>AT $\theta$<sub>1</sub> = 42$^\circ$,<br/><br/>Range, ${R_1} = {{{u^2}\sin 2(42)^\circ } \over g} = {{0.99{u^2}} \over g}$<br/><br/>At $\theta$<sub>2</sub> = 48$^\circ$ <br/><br/>Range, ${R_2} = {{{u^2}\sin 2(48)^\circ } \over g} = {{0.99{u^2}} \over g}$<br/><br/>The range of the projectile is same for the two projectiles.<br/><br/>Therefore, R<sub>1</sub> = R<sub>2</sub><br/><br/>Now, as we know the expression of height of the projectile,<br/><br/>${H_{\max }} = {{{u^2}\sin \theta } \over {2g}}$<br/><br/>At 42$^\circ$, $${H_{\max }} = {H_1} = {{{u^2}\sin 42^\circ } \over {2g}} = {{0.669{u^2}} \over {2g}}$$<br/><br/>At 48$^\circ$, $${H_{\max }} = {H_2} = {{{u^2}\sin 48^\circ } \over {2g}} = {{0.743{u^2}} \over {2g}}$$<br/><br/>Higher the value of $\theta$ higher the value of maximum height. Therefore, H<sub>1</sub> < H<sub>2</sub>.

About this question

Subject: Physics · Chapter: Kinematics · Topic: Motion in a Straight Line

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