Classical Mechanics Answers

1. The hot-air balloon contains air having a temperature of 80 degrees Celsius, while the surrounding air has a temperature of 20 degrees Celsius. Determine the volume of hot air if the total mass of the balloon and the load is 770 kg. 

2.Water in the container is originally at a height of h = 1m. If a block having a density of 800 kg/m³ is placed in the water, determine the new level h of the water. The base of the block is 600 mm square, and the base of the container is 1.2 m square.

The frequency range of audible sound is [Best

answerl.

A. lower than 20 Hz.

B. lower than 20 KHz.

C. between 20 Hz to 20 KHz.

D. greater than 20 MHz.

[Best answer] is NOT electromagnetic wave.
A. Light
B. Microwaves
C. X-rays
D. Sound wave

An apple is falling down from a height of 20m and then hit a

person. Assume that the mass of the apple is 200g. The

duration of impact is 0.001 sec and that the area of the

bone is 1 cm². (a) Calculate the impulsive force applied to

the person. (b) If the rupture strength for body tissue is

about 5 X 10⁶ dyn/cm² will the impact force lead to serious

injury for the person?

In a car collision, the bag expands suddenly and cushions

the impact of the passenger. Assume the impact velocity is

105 km/h. For a 70-kg person with a 30-cm allowed

stopping distance, (a) calculate the stopping force per cm²

applied to the person, if the average applied force is

uniformly distributed over a 1000-cm² area of the

passenger's body. (b) calculate the duration of the collision

between the passenger and the inflated bag of the collision

protection device. (c) If the rupture strength for body tissue

is about 5 X 10⁶dyn/cm², will the impact force lead to

serious injury for the passenger?

Sound waves in air are [Best answer].

A. Transverse waves

B. Longitudinal waves

C. Shear waves

D. Stress waves

A

surface of the earth. When the satellite orbits around the earth at a height equal to the diameter of the earth (above the surface of the earth), the magnitude of the gravitational force on the satellite will be:

satellite experiences a gravitational force with magnitude F when it is on the

A 3F

B 2F

C 1/3 F

D 1/9 F

Consider the following statements with regard to Newton’s third law of motion:

I: The resultant of an action-reaction force pair is zero.

II: An object moves when the action force is larger than the reaction force.

III: The resultant of an action-reaction force pair cannot be determined, because

the force acts on different objects.

Which statement(s) above is/are correct?

A Only I

B Only II

C Only III

D Only II & III

A block with a mass of 0.20 kg is hung at the end of a spring and it is lifted vertically so that the spring is unstretched. The block is then realesed and it touches the table with a velocity of 0.80 m s-1. If the distance of the table from the realesed point of the spring is 0.10 m, what is the force constant of the spring?

Consider two steel balls. Ball 1 has a

weight of 1.5 N. Ball 2 has a weight

of 15 N. Both balls are released

simultaneously from a height of 2.0 m.

Which ball hits the ground first?

a) Ball 1 hits the ground first.

b) Ball 2 hits the ground first.

c) Both balls hit the ground at the

same time.

d) It can’t be determined from the

information provided.

I think that the answer will be (b) because the answer (c) will be right only if ignore the air resistance.

I got an answer before which is (c).

Why is that?

Thank you so much.