A particle has an initial velocity 3 i +4 j and an acceleration of 0.4 i +0.3 j . Its speed after 10 s is

Correct answer: B. 7 2 units aligned u & =3 i +4 j ; a =0.4 i +0.3 j u & = u + a t & =3 i +4 j +(0.4 i +0.3 j ) 10=3 i + j +4 i +3 j =7 i +7 j aligned Speed is 7^2+7^2 =7 2 units

JEE Main 2009

Exam: JEE Main
Year: 2009
Subject: Physics
Chapter: Motion in One Dimension

JEE Main 2009 · Physics · Motion in One Dimension

A particle has an initial velocity 3 i +4 j and an acceleration of...

A particle has an initial velocity

3 \hat{i}+4 \hat{j}

and an acceleration of

0.4 \hat{i}+0.3 \hat{j}

. Its speed after 10 s is

Options

A10 units
B $7 \sqrt{2}$ units
C7 units
D $8.5$ units

Correct answer

B. $7 \sqrt{2}$ units

Step-by-step solution

\begin{aligned} \overrightarrow{\mathrm{u}}& =3 \hat{\mathrm{i}}+4 \hat{\mathrm{j}} ; \overrightarrow{\mathrm{a}}=0.4 \hat{\mathrm{i}}+0.3 \hat{\mathrm{j}} \\ \overrightarrow{\mathrm{u}}& =\overrightarrow{\mathrm{u}}+\overrightarrow{\mathrm{a}} \mathrm{t}\\ & =3 \hat{\mathrm{i}}+4 \hat{\mathrm{j}}+(0.4 \hat{\mathrm{i}}+0.3 \hat{\mathrm{j}}) 10=3 \hat{i}+\hat{\mathrm{j}}+4 \hat{\mathrm{i}}+3 \hat{\mathrm{j}}=7 \hat{\mathrm{i}}+7 \hat{\mathrm{j}} \end{aligned}

Speed is

\sqrt{7^2+7^2}=7 \sqrt{2}

units

Practice Motion in One Dimension on Quantrex Academy →

More from Motion in One Dimension

A gas balloon is going up with a constant velocity of 10 m/s. When this balloon reached a… JEE Main 2026 Two masses of 3.4 kg and 2.5 kg are accelerated from an initial speed of 5 m/s and 12… JEE Main 2026 The velocity ( v ) versus time ( t ) plot of a particle is shown in the figure, for a… JEE Main 2026 From 18 m height above the ground a ball is dropped from rest. The height above the… JEE Main 2026 Two cars A and B are moving in the same direction along a straight line with speeds 100… JEE Main 2026 The velocity of a particle is given as v = -x i + 2y j - z k m/s. The magnitude of… JEE Main 2026 A particle starts moving from time t=0 and its coordinate is given as x(t)=4 t^ 3 -3 t A.… JEE Main 2026 Water drops fall from a tap on the floor, 5 m below, at regular intervals of time, the… JEE Main 2026 Full Motion in One Dimension list All JEE Main PYQs