Easy INTEGER +4 / -1 PYQ · JEE Mains 2021

A ball weighing 10 g is moving with a velocity of 90 ms$-$1. If the uncertainty in its velocity is 5%, then the uncertainty in its position is ___________ $\times$ 10$-$33 m. (Rounded off to the nearest integer)

[Given : h = 6.63 $\times$ 10$-$34 Js]

Answer (integer) 1

Solution

m = 10 g = 10<sup>$-$2</sup> Kg<br><br>v = 90 m/sec.<br><br>$\Delta$ = v $\times$ 5% = 90 $\times$ ${5 \over {100}}$ = 4.5 m/sec<br><br>m . $\Delta$v . $\Delta$x $\ge$ ${h \over {4\pi }}$<br><br>10<sup>$-$2</sup> $\times$ 4.5 $\times$ $\Delta$x $\ge$ ${{6.63 \times 3 \times {{10}^{ - 34}}} \over {4 \times {{22} \over 7}}}$<br><br>$\Delta$x $\ge$ $${{6.63 \times 7 \times 2 \times {{10}^{ - 34}}} \over {9 \times 4 \times 22 \times {{10}^{ - 2}}}}$$<br><br>$\Delta$x $\ge$ 1.17 $\times$ 10<sup>$-$33</sup> = x $\times$ 10<sup>$-$33</sup><br><br>x = 1.17 $\simeq$ 1

About this question

Subject: Chemistry · Chapter: Atomic Structure · Topic: Bohr's Model

This question is part of PrepWiser's free JEE Main question bank. 122 more solved questions on Atomic Structure are available — start with the harder ones if your accuracy is >70%.

Drill 25 more like these. Every day. Free.

PrepWiser turns these solved questions into a daily practice loop. Chapter-wise drills, full mocks, AI doubt chat. No auto-renew.

Start free →