JEEPhysics

Center of Mass and System of Particles

12 JEE Physics previous year questions on Center of Mass and System of Particles — options free on every question; 1 include the answer & explanation free, the rest unlock with PYQ Pass.

Q1 FREE PREVIEW
PYQ
A moving block having mass m, collides with another stationary block having mass 4m. The lighter block comes to rest after collision. When the initial velocity of the lighter block is v, then the value of coefficient of restitution (e) will be:
a0.8
b0.4
c0.5
d0.25
✓ Correct answer: d) 0.25
ExplanationMass of first block (m1) = m Mass of second block (m2) = 4m Initial velocity of first block (u1) = v Since second block (heavier black) is stationary initially, Initial velocity of second block (u2) = 0 Initial momentum of the system After collision, the first block (lighter block) comes to rest, So final velocity of first block (V1) = 0 Final velocity of second block = V2 Final momentum of the system Since there is no external force on the system, so momentum of the system will remain constant Initial momentum (P1) = Final momentum (P2) mv = 4m v2 v2 = v/4 Now use the formula; Thus coefficient of restitution (e) =1 / 4=0.25
Q2
PYQ

A disc of radius 20 cm has its center at origin. If a disc of radius 5 cm is cut from it such that its edge touches the edge of the bigger disc, find the location of centre of mass of the new system.

(Shift I Memory Based)

a

(-1 cm, 0 cm)

b

(-1 cm, -1 cm)

c

(1 cm, 1 cm)

d

(1cm, - 1 cm)

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Q3
PYQ

A nucleus at rest disintegrates into two smaller nuclei with their masses in the ratio of \(2: 1\). After disintegration they will move :

[JEE Main 2024, 09 Apr (Shift 2)]

a

in opposite directions with the same speed.

b

in the same direction with same speed.

c

in opposite directions with speed in the ratio of \(2: 1\) respectively.

d

in opposite directions with speed in the ratio of \(1: 2\) respectively.

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Q4
PYQ

A nucleus at rest disintegrates into two smaller nuclei with their masses in the ratio of \(2: 1\). After disintegration they will move :

[JEE Main 2024, 09 Apr (Shift 2)]

a

in opposite directions with the same speed.

b

in the same direction with same speed.

c

in opposite directions with speed in the ratio of \(2: 1\) respectively.

d

in opposite directions with speed in the ratio of \(1: 2\) respectively.

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Q5
PYQ

Consider a circular disc of radius 20 cm with centre located at the origin. A circular hole of radius 5 cm is cut from this disc in such a way that the edge of the hole touches the edge of the disc. The distance of centre of mass of residual or remaining disc from the origin will be:

[JEE Main 2025, 23 Jan (Shift 1)]

a

0.5 cm

b

2.0 cm

c

1 .5 cm

d

1 .0 cm

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Q6
PYQ

Consider a circular disc of radius 20 cm with centre located at the origin. A circular hole of radius 5 cm is cut from this disc in such a way that the edge of the hole touches the edge of the disc. The distance of centre of mass of residual or remaining disc from the origin will be

[JEE Main 2025, 23 Jan (Shift 1)]

a

0.5 cm

b

2.0 cm

c

1 .5 cm

d

1 .0 cm

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Q7
PYQ

Consider a circular disc of radius 20 cm with centre located at the origin. A circular hole of radius 5 cm is cut from this disc in such a way that the edge of the hole touches the edge of the disc. The distance of centre of mass of residual or remaining disc from the origin will be:

a

0.5 cm

b

2.0 cm

c

1 .5 cm

d

1 .0 cm

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Q8
PYQ

A disc of radius 20 cm has its center at origin. If a disc of radius 5 cm is cut from it such that its edge touches the edge of the bigger disc, find the location of centre of mass of the new system.

(Shift I Memory Based)

a

(-1 cm, 0 cm)

b

(-1 cm, -1 cm)

c

(1 cm, 1 cm)

d

(1cm, - 1 cm)

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Q9
PYQ

A block moving horizontally on a smooth surface with a speed of 40 m/s splits into two parts with masses in the ratio of \(1:2\). If the smaller part moves at 60 m/s in the same direction, then the fractional change in kinetic energy is:

[JEE Main 2021, 31 Aug (Shift 2)]

a

\(\frac{1}{3}\)

b

\(\frac{2}{3}\)

c

\(\frac{1}{8}\)

d

\(\frac{1}{4}\)

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Q10
PYQ

A projectile is thrown from a point \(\mathrm{O}\) on the ground at an angle \(45^{\circ}\) from the vertical and with a speed \(5 \sqrt{2} \mathrm{~m} / \mathrm{s}\). The projectile at the highest point of its trajectory splits into two equal parts. One part falls vertically down to the ground, \(0.5 \mathrm{~s}\) after the splitting. The other part, \(t\) seconds after the splitting, falls to the ground at a distance \(x\) meters from the point \(O\). The acceleration due to gravity \(\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2\).The value of t is ___.

[JEE Advanced 2021]

a

0.3

b

0.4

c

0.5

d

0.6

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Q11
PYQ

A rubber ball is released from a height of \( 5 \mathrm{~m} \) above the floor. It bounces back repeatedly, always rising to \( \frac{81}{100} \) of the height through which it falls. Find the average speed of the ball. (Take \( \mathrm{g}=10 \mathrm{~ms}^{-2} \) )

[JEE Main 2021, 17 Mar (Shift 2)]

a

\( 2.50 \mathrm{~ms}^{-1} \)

b

\( 3.0 \mathrm{~ms}^{-1} \)

c

\( 2.0 \mathrm{~ms}^{-1} \)

d

\( 3.50 \mathrm{~ms}^{-1} \)

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Q12
PYQ

A rubber ball is released from a height of \( 5 \mathrm{~m} \) above the floor. It bounces back repeatedly, always rising to \( \frac{81}{100} \) of the height through which it falls. Find the average speed of the ball. (Take \( \mathrm{g}=10 \mathrm{~ms}^{-2} \) )

a

\( 2.50 \mathrm{~ms}^{-1} \)

b

\( 3.0 \mathrm{~ms}^{-1} \)

c

\( 2.0 \mathrm{~ms}^{-1} \)

d

\( 3.50 \mathrm{~ms}^{-1} \)

🔒
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