Question

1. Which of the following is true for angular motion?

a. A uniform net torque always causes an increase in angular speed.
b. A uniform net torque always changes the direction of the angular displacement vector.
c. A uniform net torque always change the magnitude of the rotational inertia.
d. A uniform net torque will always cause a change of angular momentum.

2. A net (non-zero) force acts on a particle. Which of the following does not have to be true?

a. The speed must change.
b, The particle must be accelerated.
c. The velocity must change.
d. The momentum must change.

3. Two sound waves have identical wavelength and frequency. Which of the following must also be the same for the two waves?

a. Their speed
b. Their amplitude
c. Their period
d. Two of the above answers are correct

4. Two sound waves have the same frequency and wavelength, but wave 1 has twice the amplitude of wave 2. Which of the following must be true?

a. They are moving at different speeds
b. The have the same energy per wavelength
c. They have different media in which the travel
d. The energy per wavelength of each is different
e. None of the above is true

Answer 1

1) if there is net angular torque there will be change in angular momentum

and torque = rate of change of angular momentum

so option d) is the correct answer

2) according to Newton's second law we have

force = rate of change of momentum

so if there is a net force, momentum will change

so option d) is correct

3) speed = wavelength * frequency

if both are same, speed will be the same

so a) Their speed is the correct answer

4) energy of a wave is proportional to the square of amplitude

so the energy per wavelength of each is different

so option d) is the correct answer