# NCERT Class-9 Science Solutions: Chapter 9-Force And Laws Of Motion Part 4

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**Question 19:**

Derive the unit of force using the second law of motion. A force of produces an acceleration of on a mass and an acceleration of on a mass . What acceleration would the same force provide if both the masses are tied together?

**Answer:**

This unit is also called newton. Its symbol is N.

Acceleration produced in M,

**Question 20:**

What is momentum? Write its SI unit. Interpret force in terms of momentum. Represent the following graphically

**Answer:**

SI unit of momentum is

Force = Rate of change in momentum

Momentum versus velocity when mass is fixed

Momentum versus mass when velocity is constant