## Moment of inertia equation

3 Problems and solutions about Moment of inertia equation

1. A solid cylinder has a radius of 8 cm and a mass of 2 kg. Meanwhile, a solid ball has a radius of 5 cm and a mass of 4 kg. If the two objects rotate with an axis through their center, determine the ratio of the moment of inertia of the cylinder and the ball.

Known:

Solid cylinder radius (r) = 8 cm = 0.08 m

Solid cylinder mass (m) = 2 kg

Solid ball radius (r) = 5 cm = 0.05 m

The mass of the solid ball (m) = 4 kg

Wanted: Comparison of the moment of inertia of a cylinder and a ball

Solution:

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## Momentum equation

3 problems and solutions about Momentum equation

1. If the object’s speed becomes 5 times its original speed, then the object’s momentum becomes ….. its original momentum.

Known:

Initial speed = v

Final speed = 5v

Mass = 1

Wanted: Momentum

Solution:

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## Speed equation

3 problems and solutions about the Speed equation

1. A car travels to the south for 100 m in 1 minute then turns to the east 120 m in 0.5 minutes. Determine the average speed of the car.

Known:

Total distance = 100 meters + 120 meters = 220 meters

Total time = 1 minute + 0.5 minutes = 1.5 minutes = 90 seconds

Wanted: Average speed

Solution:

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## Parabolic motion Work and kinetic energy Linear momentum Linear and angular motion Problems and Solutions

### 5 Parabolic motion Work and kinetic energy Linear momentum Linear and angular motion Problems and Solutions

1. A ball is thrown from the top of a building with an initial speed of 8 m/s at an angle of 20o below the horizontal. The ball hits the ground 3 seconds later.

a) How far from the bottom of building the ball touches the ground

b) How high is the ball thrown from the place

c) How long the ball reaches a height of 10 m from the place of throwing

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## Transverse waves – problems and solutions

1. The distance between the two troughs of the water surface waves is 20 m. An object floats on the surface of the water so that it experiences the vibration motion. If the time to travel one vibration is 4 seconds, then the velocity of the wave is …. m/s

A. 20

B. 15

C. 10

D. 5

Known :

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## Speed of the mechanical waves – problems and solutions

1. The speed of the transverse wave on a 25 meters rope is 50 m/s. The tension force of the rope is 200 N. Determine the mass of rope.

A. 0.08 kg

B. 0.5 kg

C. 0.8 kg

D. 2.0 kg

Known :

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## Simple harmonic motion – problems and solutions

1. An object vibrates with a frequency of 5 Hz to rightward and leftward. The object moves from equilibrium point to the maximum displacement at rightward. Determine the time interval required to reach the maximum displacement at rightward eleven times.

A. 2.05

B. 2.20

C. 2.25

D. 2.50

Known :

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## Simple pendulum – problems and solutions

1. Two simple pendulums are in two different places. The length of the second pendulum is 0.4 times the length of the first pendulum, and the acceleration of gravity experienced by the second pendulum is 0.9 times the acceleration of gravity experienced by the first pendulum. Determine the comparison of the frequency of the first pendulum to the second pendulum.

A. 2/3

B. 3/2

C. 4/9

D. 9/4

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## Resonance of sound wave – problems and solutions

1. After the tuning fork A is vibrated, the tuning fork B is vibrated. The tuning fork B is vibrated because…..

A. The tuning fork A has the same amplitude as the tuning fork B

B. Both tuning forks use the same resonance box

C. The tuning fork B has the same frequency as the tuning fork A

D. The timbre of the sounds caused by both tuning forks are the same

Solution

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## Pressure of fluids – problems and solutions

1.

Acceleration due to gravity is 10 N/kg. The surface area of fish pressed by the water above it is 6 cm2. Determine the force of water above fish that acts on fish.

Known :

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