**Laws of Motion Exe-3C** **Linear Momentum Newton’s Second Law** **Very Short Answer** Type for Class-9 ICSE Concise Physics. There is the solutions of **Very short Answer** type Questions of your latest textbook which is applicable in 2023-24 academic session**. **Visit official Website CISCE for detail information about ICSE Board Class-9.

**Laws of Motion Exe-3C Linear Momentum Newton’s Second Law Very Short Answer **

**(ICSE Class – 9 Physics Concise Selina Publishers)**

Board | ICSE |

Class | 9th |

Subject | Physics |

Writer / Publication | Concise selina Publishers |

Chapter-3 | Laws of Motion |

Exe – 3C | Linear Momentum Newton’s Second Law |

Topics | Solution of Exe-3(C) Very Short Answer Type |

Academic Session | 2023-2024 |

**Exe-3C Linear Momentum Newton’s Second Law Very Short Answer Type**

**Ch-3 Laws of Motion Physics Class-9 ICSE Concise**

**Page 77**

**Question 1. **Define linear momentum and state its S.I. unit.

**Answer :**

Linear momentum of a body is the product of its mass and velocity.

Its SI unit is kgms^{-1}.

**Question 2. **A body of mass *m *moving with a velocity *v *is acted upon by a force. Write an expression for change in momentum in each of the following cases: (i) When *v * <<c, (ii) When *v →*c and (iii) When *v <<* c but *m *does not remain constant. Here, c is the speed of light.

**Answer :**

(i) When *v * <<c,

p = (mv) = mv

(ii) When *v →*c

p = (mv)

(iii) When *v <<* c but *m *does not remain constant.

p = (mv)

**Question 3.**Two bodies *A *and *B *of same mass are moving with velocities *v *and *2v, *respectively. Compare their (i) inertia and (ii) momentum.

**Answer:**

(i) Mass is the measure of inertia.

Let ‘m’ be the mass of the two bodies.

Inertia of body A:Inertia of body B :: m:m

Or, Inertia of body A:Inertia of body B :: 1:1

(ii)

Momentum of body A = m (v)

while Momentum of body B = m (2v) = 2mv

hence Momentum of body A:Momentum of body B :: mv:2mv

Or, Momentum of body A:Momentum of body B :: 1:2.

**Question 4. **Two balls *A *and *B *of masses *m *and 2 *m *are in motion with velocities *2v *and *v, *respectively. Compare:

(i) Their inertia.

(ii) Their momentum.

(iii) The force needed to stop them in the same time.

**Answer:**

(i) Inertia of body A:Inertia of body B :: m:2m

Or, Inertia of body A:Inertia of body B :: 1:2.

(ii)

Momentum of body A = m ( 2v) = 2mv

and Momentum of body B = (2m) v = 2mv

Hence Momentum of body A:Momentum of body B :: 2 mv:2mv

Or, Momentum of body A:Momentum of body B :: 1:1.

(iii) According to Newton’s 2^{nd} law of motion, rate of change of momentum is directly proportional to the force applied on it. Therefore,

Force needed to stop A:Force needed to stop B :: 1:1.

**(Laws of Motion Exe-3C Very Short Class-9 ICSE)**

**Question 5. **Name the S.I. unit of force and define it.

**Answer:**

The S.I. unit of force is newton.

One newton is the force which acts on a body of mass 1kg and produces an acceleration of 1 m/s^{2}, i.e. 1 N = 1 kg × 1 m/s^{2}.

**Question 6. **What is the C.G.S. unit of force? How is it defined?

**Answer:**

The C.G.S. unit of force is dyne.

One dyne is the force which acts on a body of mass 1 gramme and produces an acceleration of 1 cms^{-2}, i.e. 1 dyne = 1 g × 1 cms^{-2}.

**Question 7. **Name the S.I. and C.G.S. units of force. How are they related?

**Answer:**

The S.I. unit of force is newton and the C.G.S. unit of force is dyne.

1 N = 10^{5} dyne.

— : End of Laws of Motion Exe-3C **Linear Momentum Newton’s Second Law** Very Short Answer Type Solutions :–

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