BoardPhysics

Laws of Motion

3 Board Physics previous year questions on Laws of Motion — options free on every question; 1 include the answer & explanation free, the rest unlock with PYQ Pass.

Q1 FREE PREVIEW
PYQ

A massless spring gets elongated by amount \({x}_{1}\) under a tension of 5 N . Its elongation is \({x}_{2}\) under the tension of 7 N . For the elongation of \(\left(5{x}_{1}-2{x}_{2}\right)\), the tension in the spring will be,

[JEE Main 2025, 23 Jan (Shift 2)]

a

39 N

b

15 N

c

20 N

d

11 N

✓ Correct answer: d)

11 N

Explanation

\({F}_{1}=k{x}_{1}\\ 5=k{x}_{1}\\ {x}_{1}=\frac{5}{k}\\ 7=k{x}_{2}\\ {x}_{2}=\frac{7}{k}\)

\(x=5{x}_{1}-2{x}_{2}\\ x=\frac{25}{k}-\frac{14}{k}\Rightarrow x=\frac{11}{k}\\ F=kx\\ F=k\times \frac{11}{k}\\ F=11N\)

Q2
PYQ

A balloon of mass M is ascending with an acceleration a. What fraction of its mass should be dropped so that it starts moving upward with an acceleration of 3 a ?

(Shift - II Memory Based)

a

\(\frac{2 a}{g+3 a}\)

b

\(\frac{a}{g+2 a}\)

c

\(\frac{2 a M}{g+3 a}\)

d

\(\frac{a M}{g+2 a}\)

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Q3
PYQ

A ball of mass \(0.15\ kg\) is dropped from a height \(10\ m\), strikes the ground and rebounds to the same height. The magnitude of impulse imparted to the ball is (\(g = 10\ m/s^{2}\)) nearly:

a

\(2.1\mathrm{kg}\mathrm{m}/\mathrm{s}\)

b

\(1.4\mathrm{kg}\mathrm{m}/\mathrm{s}\)

c

\(1.1\mathrm{kg}\mathrm{m}/\mathrm{s}\)

d

\(4.2\mathrm{kg}\mathrm{m}/\mathrm{s}\)

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