This set of Fluid Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Impulse Momentum Equation”.

1. When a cricket bat hits a cricket ball, impulse is applied on the_________

a) Bat

b) Ball

c) Bat and ball

d) No impulse is applied

View Answer

Explanation: The bat applies the force on the ball for a short period of time and hence it receives an impulse. By this way, we can say in accordance to the Newton’s third law forces come in pairs. So, the ball also applies a force on the bat, therefore it has an impulse applied to it.

2. Momentum is a ______ quantity

a) Scalar

b) Vector

c) Infinite

d) Zero

View Answer

Explanation: Momentum is a vector quantity as it has both size and direction. Size of the momentum is equal to the mass of the object into the size of the objects velocity. The direction of objects velocity is the same as the direction of the momentum.

3. The equation for impulse is_______

a) F∆t=m∆v

b) F∆t=mu

c) F∆t=mT

d) F∆t=mRT

View Answer

Explanation: Impulse is equal to the net force times the length of time over which the force is applied on the body of the fluid. On the right hand side, we have the change in momentum. Thus, option ‘a’ is the most suitable one.

4. What is the SI unit of impulse?

a) N/m

b) N/m^{2}

c) N.s

d) Kg.m

View Answer

Explanation: The SI unit of impulse is Newton second. It is given by the linear momentum due to the vector change. This produces an impulse in the same direction with respect to a given time.

5. What is the SI unit of momentum?

a) kgm/s

b) kgm/s^{2}

c) kgm/s^{3}

d) kg.m^{2}

View Answer

Explanation: The SI unit of momentum is given by the product of the units of mass and velocity. In SI units, (mass is in kg) and (velocity is in m/s). As we know that momentum is mass times velocity. The unit turns out to be kgm/s.

6. Change in momentum of an object is equal to the_______

a) Internal Energy

b) Entropy

c) Impulse

d) Enthalpy

View Answer

Explanation: The mass is distributed over two velocities. According to the Newton’s second law, the change in momentum is equal to the impulse so produced. Since, momentum is a quantity that describes an object’s resistance to stopping. It is equated with its impulse.

7. What is the unit of specific impulse?

a) m/s

b) m^{2}/s

c) m^{3}/s

d) m/s^{2}

View Answer

Explanation: Specific impulse is equal to the exhaust velocity of the fluid. Since, the unit of exhaust velocity is m/s, the unit of specific impulse is also the same. It is used to measure the efficacy of rocket propellants.

8. What is the formula to find specific impulse?

a) J_{sp}=m/v

b) J_{sp}= J/m

c) J_{sp}=T/m

d) J_{sp}=J/q

View Answer

Explanation: Specific impulse is defined as impulse per weight. It can also be defined as thrust per weight of a flow rate. It is equal to the exhaust velocity divided by acceleration due to gravity. (SI Unit: m/s)

9. Angular momentum is a _______ quantity

a) Scalar

b) Vector

c) Infinite

d) Finite

View Answer

Explanation: Angular momentum is a vector quantity as it has both size and direction. Size of the momentum is equal to the mass of the object into the size of the object’s velocity. The direction of objects velocity is the same as the direction of the momentum.

10. Angular momentum is proportional to __________

a) Inertia and angular speed

b) Mass and angular speed

c) Angular speed and volume

d) Rate of change of angular speed

View Answer

Explanation: Moment of inertia is not only dependent on the amount of matter. It also depends upon the position of axis of rotation and the shape of the matter. (Formula: L=Iω). Thus, inertia and angular speed play an important role in determining the angular momentum.

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