Physics Essay: Questions And Answers.

Question 1

1. Can an object reverse its direction of travel while maintaining a constant acceleration? If so, cite an example. If not, provide an explanation.

2. Can an automobile with a velocity toward the north simultaneously have an acceleration towards the south? Please explain your answer.

3. You toss a ball straight up with an initial speed of 20m/s. How much time does it take to reach its maximum height (ignoring air resistance)?

4. A car slows down from 28 m/s to rest in a distance of 88m. What was its acceleration, assumed constant?

5. Suppose that you jounce up and down while weighing yourself on a bathroom scale. Which varies: the upward support force or the force of gravity on you? Why is your weight reading best shown when you stand at rest on the scale?

6. A crater remains at rest on a factory floor while you push on it with 100 N of horizontal force. What is the friction force exerted on the crate by the floor? Please explain your answer.

7. If a lorry and a car have a head-on collision, upon which vehicle is the impact force greater? Which vehicle experiences the greater deceleration? Please explain your answer.

8. Why must you bend forward when carrying a heavy load on your back?

9. One man is twice as tall as another man. Assume that they are completely similar in other characteristics of their body and doing exactly the same stationary gymnastic maneuver. Are they subjected to the same stresses in their bones and muscles? Explain your answer.

10. If an elderly person with osteoporosis falls and is then diagnosed with a broken hip, in what way could the osteoporosis have contributed to the breaking?

11. Are you slightly longer while lying down than you are tall when you are standing up? Please explain your answer.

12. The mechanical properties of bone material are anisotropic. Please use examples to explain what this means.

13. If an erect person's systolic pressure is measured at 120 mm-Hg at the level of heart, please calculate the arterial systolic blood pressure in the feet of this person (in the unit of mm-Hg). Assume that the heart is 130 cm above the feet (the density of blood is 1050 kg/m3), and 1 mm-Hg = 133 N/m2

14. When you are standing, blood pressure in your legs is greater than in your upper body. Would this be true for an astronaut in orbit? Defend your answer.

15. Why bodies float higher in saltwater than in fresh water?

16. Computer the average velocity of the blood in the aorta of radius 1cm if the flow rate is 5 litre/min.

17. If the speed of a wave doubles while the frequency remains the same, what happens to the wavelength? Please explain your answer.

18. When you blow your horn while driving toward a stationary listener, the listener hears an increase in the frequency of the horn. Would the listener hear an increase in the horn frequency if he or she were also in a car traveling at the same speed in the same direction as you are? Please explain your answer.

19. If the speed of sound were dependent on its frequency, would you enjoy a concert sitting in the second balcony? Please explain your answer.

20. A cat can hear sound frequencies up to 70,000 Hz. Bats send and receive ultra-high-frequency squeaks up to 120,000 Hz. Which hears sound of shorter wavelengths: cats or bats. Please explain your answer.

Question 1

It is possible for an object to reverse its direction at a constant acceleration. This applies to objects that are traveling in a straight line and circular path. Upon changing direction instantaneous velocity or speed is equal but in a different direction. For an object in orbit, it will change direction forming a tangent with the radius. Constant acceleration is achieved when a change in velocity is of an equal amount with an equal change in time. For example, if a stone is thrown upwards it will move downwards at a constant acceleration due to gravitational pull.

Question 2

Yes. The speed at which the automobile is traveling is its velocity. If there is an increase in speed as it travels northwards, then it is accelerating. If the speed decreases, then it is accelerating to an opposite direction. This means that by a traveling automobile decreasing its speed it will be regarded as accelerating towards the south.

Question 3

From the formula the square of final velocity is equal the square of initial velocity minus 2 times gravity times height.

v²= u² - 2gh

Where g is gravity, u is initial velocity, v is final velocity and h is the displacement.

At the height where the object changes the direction the velocity will be zero.

At maximum height v = 0m/s 

This therefore means that final velocity in our case will be zero. Thus, gives the equation

0 = u² – 2gh, therefore

Which can be a rearranged to form

u² = 2gh, thus

h = u²/2g

substituting the values in the above formula gives

20²/*9.8 = 40.82m

Question 4

Using the formula displacement equals square of initial velocity divide two times acceleration.

s = u²/2a,

where: a is acceleration, u is initial velocity and s is displacement. 

This can be rearranged to give acceleration equals initial speed squared divided by two times displacement

therefore, a = u²/2s

replacing the values given in the above formula gives

28²/2*88 = 4.455m/s²

The acceleration of the car will thus be 4.455m/s² as it slows from 28m/s to rest after traveling for 88m.

Question 5

When jouncing the force of gravity acting on the body when up and that acting on the body when down are not equal. This is due to the action and reaction forces on the body which is generated by gravity fluctuations. When standing at rest, the two forces are equal as the gravity acting on the body is constant. The scale therefore will give a more reliable and accurate measure of your weight.

Question 2

Question 6

The definition of friction is that it is the resistant force that a body encounters whenever it is moving over another body. When a crater remains at rest when being pushed by a force of  then the resultant friction being exerted on the crater by the floor is zero. Reason is that no object is moving against another in this case hence no friction.

Question 7

Impact force is greater on the car. The car experiences a greater deceleration. The lorry being heavier than the car hence greater force will originate from the lorry. Assuming, 1000N for lorry and 90N for the car. The resultant force upon impact will be towards the side of the car. The higher force generated b the lorry will be impacted by the car this makes the impact greater on the car. This will therefore generate a resultant force that will push the car backward hence leading to deceleration of the car.

Question 8

For a body to balance the center of gravity must be restored in a central position since it is the one responsible for the body’s uprightness.

When upright, the load adds weight towards one’s back hence interfering with the original center of gravity. The center of gravity will thus be displaced from the central position. This will lead to pulling the individual backward. Bending forward restores the center of gravity to center of the body. This way the individual can avoid falling by maintaining his/her body balance.

Question 9

Work done is equal to distance multiplied by force. Gravity will act on all the two bodies equally. At a constant gravitational force, the distance the two covers are different during their process of gymnast maneuver be3caquse of the difference in their heights. This shows that the work done by the taller person is more than the work done by the shorter person.

Question 10

As individuals grow old their bines wear out a situation that can develop into a condition called Osteoporosis. This situation is more prominent in women than men since their bones are lighter than that of men. Osteoporosis makes the bones brittle therefore they can break more easily. Brittle materials do not absorb much energy this way they are broken easily accompanied by a snapping sound whenever force is applied to them. this way the condition may have catalyzed the breaking of the bones when the old man felt.

Question 3

Question 11

Yes. Gravity is a force that attracts bodies towards the center of the earth. When standing the force will press the body downwards hence making an individual slightly shorter. Gravitational pull brings the effect. When standing the joints in our bodies are compressed by gravity force pulling various body parts thus lowering the height. When lying, the stress on the joint by gravity is absent thus one becomes taller. This is because a lying body experiences gravity, but the force is applied in a way that does not interfere with the person height since the body parts are not pressed vertically. Instead, the force will act on the body horizontally hence having no effect on the height.

Question 12

Anisotropic is a substance that has a physical property which possesses diverse values when measured at different angles. For instance, wood is stronger along the grain than it is across the grain. This simply means that the properties of the property vary depending on the direction the measurement is taken from. This situation reflects on the individuals’ bones which also possess different properties depending on the angle taken during the measurement process.

Question 13

Pressure is given by force times gravity times height

P = ?gh, where f is the force, g the gravity and h the height

Substituting the values given in to the formula we obtain

 1050*9.8*1.30 = 13377 N/m² 

This is farther converted to yield

 Convert N/m² into mmHg

13377/133 = 100.58 mmHg.

The pressure at the feet will therefore = 100.58 + 120

Which yield

= 220.58 mmHg. As the final value.

Question 14

No, normally blood pressure at the leg is 20 mmHg higher than in the arms. Thus, differences in pressure distribution among the body parts is brought about by the height difference. Since P = ?gh, where f is the force, g the gravity and h the height, then the difference in height will influence the magnitude of gravitational force hence the pressure level in these parts. 

At the orbit, there is no gravity. This way the formula, P = ?gh, where f is the force, g the gravity and h the height, will not apply as the zero gravity will mean pressure will be zero This means that the body is experiencing no pull by the gravity hence blood pressure at the leg will normal as other body parts.  

Question 15

Question 4

For a body to float in water then the density of the body must be lower than that of water. Addition of salt water will increase the density of water. For this reason, bodies will float higher in the salty water due to the increased density.

Question 16

Output = stroke volume * rate

Convert into cubic centimeter per second

1/100 * 5000/60 = 0.8333 cm/s

Question 17

Using the formula velocity equals wavelength multiplied frequency, we can see that speed and wavelength are directly related. For this purpose, whenever the speed doubles the wavelength will double as well. This is because of the direct relationship that is shown by the formula used.

Question 18

No, since both you and the listener are traveling at the same speed towards same direction the time that the sound will take to reach the listener will be constant. This therefore means that the frequency of the horn will remain constant as well. The listener will therefore not hear an increased frequency of the horn sound. On the case where the listener was stationary as the horn is blown nearer and nearer to him/her, the distance that the sound travels reduces thus means it reaches them faster and without a lot of losses from interference. Therefore, the listener will hear a sound with increased frequency.

Question 19

Yes. The speed of sound is dependent on the medium that produces it and not the frequency. The degree of diffraction of sound depends on its wavelength and the size of the opening the sound passes through. Diffraction is strongest and sharp where the wavelength of sound is longer or same to that of the opening. If the speed was to be dependent on the frequency, then the concert will be more enjoyable at the balcony since the frequency will be higher in that position. This means the person standing there will receive sound faster hence hears more clear and enjoyable sound.

Question 20

Bats, this is because higher frequencies indicate shorter wavelengths compared to the wavelength of lower frequencies.

Frequency can be regarded as the rate per second of a vibration involving a wave. This can be within a material like the case of sound waves or even in the electromagnetic field. On the other hand, the wavelength is simply the distance between successive crests of a wave. As the frequencies increase the crests becomes closer hence leading to a reduction in the wavelengths.