Question

8.2 conservation of momentum

1. what is angular momentum?

a. the sum of moment of inertia and angular velocity
b. the ratio of moment of inertia to angular velocity
c. the product of moment of inertia and angular
velocity
d. half the product of moment of inertia and square of
angular velocity

1. what is an isolated system?

a. a system in which the net internal force is zero
b. a system in which the net external force is zero
c. a system in which the net internal force is a nonzero
constant
d. a system in which the net external force is a nonzero
constant
8.3 elastic and inelastic collisions

1. in the equation ( p_1 + p_2 = p_1 + p_2 ) for the collision of two

objects, what is the assumption made regarding the
friction acting on the objects?
a. friction is zero.
b. friction is nearly zero.
c. friction acts constantly.
d. friction before and after the impact remains the
same.

Explanation:

• Question 5:
• Angular momentum formula is \(L = I\omega\), where \(I\) is moment of inertia and \(\omega\) is angular velocity.
• Option a: Sum \(I+\omega\) is not angular momentum.
• Option b: Ratio \(\frac{I}{\omega}\) is not angular momentum.
• Option c: Product \(I\omega\) is angular momentum.
• Option d: \(\frac{1}{2}I\omega^{2}\) is rotational kinetic energy.
• Question 6:
• An isolated system is defined as a system where net external force \(F_{ext}=0\).
• Option a: Internal forces do not define an isolated system.
• Option b: Net external force zero is correct for isolated system.
• Option c: Non - zero internal force is not relevant for isolation.
• Option d: Non - zero external force means non - isolated.
• Question 7:
• The equation \(p_{1}+p_{2}=p_{1}'+p_{2}'\) (conservation of momentum) assumes no external forces. Friction is an external force.
• Option a: If friction is zero (no external force), conservation of momentum holds.
• Option b: “Nearly zero” is not an exact assumption for the strict conservation equation.
• Option c: Constant friction would be an external force, violating conservation.
• Option d: Same friction (non - zero) still means external force, violating conservation.

Answer:

1. C. The product of moment of inertia and angular velocity
2. B. A system in which the net external force is zero
3. A. Friction is zero.