Verified Solution • 2025–26 Session moderate

QJEEM25Phc0c2: JEE Main 2025 Physics - Class 11 JEEM25Phc0c2 Solution: A body of mass 4 kg is placed on a plane at a point having…

A body of mass 4 kg is placed on a plane at a point PP having coordinate (3,4)m(3,4) \mathrm{m} . Under the action of force F→=(2i^+3j^)N\overrightarrow{\mathrm{F}}=(2 \hat{i}+3 \hat{j}) \mathrm{N} , it moves to a new point Q having coordinates (6,10)m(6,10) \mathrm{m} in 4 sec . The average power and instanteous power at the end of 4 sec are in the ratio of :

Multiple Choice Options

  • A 4:03
  • B 13:06
  • C 1:02
  • D 6:13

Step-by-Step Verified Solution

amp;⟨p⟩=(2i^+3j^)⋅(3i^+6j^)4=6amp;a→=(F→ m=12i^+34j^)amp;v→ at t=4sec=(12i^+34j^)×4=(2i^+3j^)amp;Pins =(2i^+3)(2i^+3j^)=13amp;⟨P⟩Pins =613\begin{aligned}& \langle\mathrm{p}\rangle=\frac{(2 \hat{\mathrm{i}}+3 \hat{\mathrm{j}}) \cdot(3 \hat{\mathrm{i}}+6 \hat{\mathrm{j}})}{4}=6 \\& \overrightarrow{\mathrm{a}}=\left(\frac{\overrightarrow{\mathrm{F}}}{\mathrm{~m}}=\frac{1}{2} \hat{\mathrm{i}}+\frac{3}{4} \hat{\mathrm{j}}\right) \\& \overrightarrow{\mathrm{v}} \text { at } \mathrm{t}=4 \mathrm{sec}=\left(\frac{1}{2} \hat{\mathrm{i}}+\frac{3}{4} \hat{\mathrm{j}}\right) \times 4=(2 \hat{\mathrm{i}}+3 \hat{\mathrm{j}}) \\& P_{\text {ins }}=(2 \hat{\mathrm{i}}+3)(2 \hat{\mathrm{i}}+3 \hat{\mathrm{j}})=13 \\& \frac{\langle\mathrm{P}\rangle}{P_{\text {ins }}}=\frac{6}{13}\end{aligned}

Note: Given data is not matching.

amp;S=ut+12at2amp;S=0+12(2i^+3j^)4(4)2=4i^+6j^\begin{aligned}& S=u t+\frac{1}{2} a t^2 \\& S=0+\frac{1}{2} \frac{(2 \hat{i}+3 \hat{j})}{4}(4)^2=4 \hat{i}+6 \hat{\mathrm{j}}\end{aligned}

If r→i=3i^+4j^\overrightarrow{\mathrm{r}}_{\mathrm{i}}=3 \hat{\mathrm{i}}+4 \hat{\mathrm{j}} then r→f=7i^+10j^\overrightarrow{\mathrm{r}}_{\mathrm{f}}=7 \hat{\mathrm{i}}+10 \hat{\mathrm{j}}

But Final position given in the question is (6,10)(6,10) .

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