A particle is moving eastwards with a velocity of $5 \mathrm{~m} / \mathrm{s}$ in 10 seconds the velocity changes to $5 \mathrm{~m} / \mathrm{s}$ northwards. The average acceleration in this time is

(D) $\frac{1}{\sqrt{2}} \mathrm{~m} / \mathrm{s}^{2}$ towards north-west

(A) $\frac{1}{\sqrt{2}} \mathrm{~m} / \mathrm{s}^{2}$ towards north-east

(B) $\frac{1}{2} \mathrm{~m} / \mathrm{s}^{2}$ towards north.

JEE Main · 2005 · 08 May 2005 · Offline · Kinematics

A particle is moving eastwards with a velocity of

5 m / s

in 10 seconds the velocity changes to

5 m / s

northwards. The average acceleration in this time is

(A) $\frac{1}{2} m / s^{2}$ towards north-east
(B) $\frac{1}{2} m / s^{2}$ towards north.
(C)zero
(D) $\frac{1}{2} m / s^{2}$ towards north-west✓ Correct

Answer: (D)

Solution

The velocity turns from

5 \hat{i}

(east) to

5 \hat{j}

(north), so the change is

Δ v = 5 \hat{j} - 5 \hat{i}

. The average acceleration is

a = \frac{Δ v}{t} = \frac{5 j ^ - 5 i ^}{10} = \frac{1}{2} (\hat{j} - \hat{i})

, of magnitude

\frac{1}{2} 1^{2} + 1^{2} = \frac{1}{2}

m/s

^{2}

. Since it points along

- \hat{i} + \hat{j}

(west and north together), the average acceleration is

\frac{1}{2}

m/s

^{2}

directed towards the north-west.

JEE Main · 2005 · 08 May 2005 · Offline · Single correct option

Practise more: all JEE Main PYQs on Kinematics →

More JEE Main questions on Kinematics

A projectile is thrown upward at an angle $6 0^{\circ}$ with the horizontal. The speed of the projectile is 20 m/s when its direction of motion is $4 5^{\circ}$ with the horizontal. The initial speed of the projectile is ______ m/s.
JEE Main 2026View solution →
A river of width 200 m is flowing from west to east with a speed of $18 km / h$ . A boat, moving with speed of $36 km / h$ in still water, is made to travel one-round trip (bank to bank of the river). Minimum time taken by the boat for thi …
JEE Main 2026View solution →
An object is projected with kinetic energy K from a point A at an angle $6 0^{\circ}$ with the horizontal. The ratio of the difference in kinetic energies points B and C to that at point A (see figure), in the absence of air friction is :
JEE Main 2026View solution →
A block is sliding down on an inclined plane of slope $θ$ and at an instant $t = 0$ this block is given an upward momentum so that it starts moving up on the inclined surface with velocity $u$ . The distance $(S)$ travelled by the block before its velocity become zero, …
JEE Main 2026View solution →
A paratrooper jumps from an aeroplane and opens a parachute after 2 s of free fall and starts deaccelerating with $3 m / s^{2}$ . At 10 m height from ground, while descending with the help of parachute, the speed of paratrooper is …
JEE Main 2026View solution →
A bead $P$ sliding on a frictionless semi-circular string $(A C B)$ and it is at point $S$ at $t = 0$ and at this instant the horizontal component of its velocity is $v$ . Another bead $Q$ of the same mass as $P$ is ejected from point $A$ at $t = 0$ …
JEE Main 2026View solution →