Showing posts with the label Physics

Inner Ear

The inner ear is a complex system of fluid-filled cavities in the temporal bone. Among these cavities are the three semicircular canals, whose function is not hearing, but rather the detection of movements of the head. The organ of the inner ear concerned with hearing is the cochlea, a tube of about 3.5 cm coiled in a tight spiral. The tube is divided lengthwise into three adjoining ducts, separated by two membranes, Reissner’s membrane, and the basilar membrane. The sensory receptor of the inner ear is the organ of Corti, consisting of thousands of hair cells, which sit on the basilar membrane. The vibrations of the oval window excite a wave motion in the fluid of the cochlea, which shakes the basilar membrane. The hair cells detect this motion of the basilar membrane and convert the mechanical energy into electric nerve impulses. The basilar membrane is stiff at the end near the oval window, and soft at the distant end. Because of this, the near part of the membrane responds most rea

Middle Ear

The middle ear is an air-filled cavity in the temporal bone of the skull. The cavity is connected to the nasopharynx by the Eustachian tube; this tube permits equalization of the air pressure in the middle ear with the external atmospheric pressure. The middle ear contains three small bones or oscines: the hammer, the anvil, and the stirrup (malleus, incus, and stapes). These ossicles are arranged in a chain from the eardrum to the oval window of the inner ear. The chain of ossicles to the oval window transmits the vibrations generated by a sound wave striking the eardrum. Since the oval window has a much smaller area than the eardrum (about 1/25), the transmission of sound energy from the eardrum to the oval window results in a significant concentration of the energy, with a consequent increase of the amplitude of vibration. Besides transmitting the vibrations from the eardrum to the oval window, the middle ear plays a crucial role in accommodating the ear to very loud sounds. In resp

How Ear Converts Sounds Into Electric Nerve Pulses

The ear performs the task of converting the mechanical oscillations of a sound wave into electric nerve impulses. Thus, it is similar to a microphone, which also converts the mechanical oscillations of sound into electric signals. However, the ear is unmatched in its ability to accommodate a wide range of intensities of sound. The human ear has three main parts: the outer ear, the middle ear, and the inner ear. The outer ear consists of the auricle and the ear canal. The auricle serves to funnel sound waves into the ear, especially waves arriving from the front of the listener. The ear canal is a tube, about 2.7 cm long, closed off at the inner end by the eardrum, or tympanum. The ear canal guides sound waves toward the eardrum, and also enhances sound waves of a frequency of a few thousand hertz, which are in resonance with the standing-wave modes of the air column in the canal.

What is sound wave?

A sound wave in air consists of alternating zones of low and high density. The vibrating diaphragm of a loudspeaker generates such zones of alternating density. The alternating zones of low density and high-density travel to the right away from the source. However, although these density disturbances travel, the air as a whole does not travel, the air molecules merely oscillate back and forth. The pushes of the loudspeaker or of the tuning fork on the air are longitudinal, and the sound wave itself is also longitudinal. The air molecules oscillate back and forth along the direction of propagation of the sound wave. The restoring force that drives these oscillations is the pressure of air. Wherever the density of molecules is higher than normal, the pressure also is higher than normal and pushes the molecules apart; wherever the density of molecules is lower than normal, the pressure also is lower than normal, and therefore the higher pressure of the adjacent regions pushes these molecu

What is Work?

To introduce the definition of work done by a force, we begin with the simple case of motion along a straight line, with the force along the line of motion, Consider a particle moving along a straight line, say, the x-axis, and suppose that a constant force F, directed along the same straight line, acts on the particle. For example, the particle might be a stalled automobile that you are pushing along a road.  Then the work done by the force F on the particle as it moves some given distance S is defined as the product of the force and the displacement, W = F. S =FSCos α where α is the angle between the force F and the displacement S. Work is a scalar quantity. The unit of work is [W] = [F] [S] In metric system, unit of work is Joule. [W] = 1 Joule = 1 N.m In CGS system, unit of work is erg. Relation between the units of work is 1 Joule = 1 N.m = 10 5 D. 10 2  cm = 10 7  ergs.

Newton’s Laws of Motion

Newton’s Laws of Motion Learning Objectives On completion of this lesson, you will be able to learn- Newton’s first law of motion Newton’s second law of motion Newton’s third law of motion. Newton's three laws of motion give the fundamental properties of force and the relationship between force and acceleration. The first of these laws describe the natural state of motion of a body on which no external forces are acting, whereas the other two laws deal with the behavior of bodies under the influence of external forces. Newton’s First Law Newton’s First Law summarizes experiments and observations on the motion of bodies on which no external forces are acting, thus the first law is - A body at rest remains at rest, and a body in motion continues to move at a constant velocity unless acted upon by an external force.  The tendency of a body to continue in its initial state of motion (a state of rest or a state of uniform velocity) is called its inertia.  Accordingly, the First Law is o

What is mass?

Mass is defined by the quantity of matter of a substance. In general, weight is used to measure an object. It is not correct, weight is the gravitational pull of the earth on the body. The mass of a body remains it everywhere, but the weight may vary. For example, the weights of a body become one-sixth of its value on the moon, since moon’s gravitation is one-sixth of the earth. But mass of the body is same.

What is velocity?

Velocity is defined as the rate of change of distance moved with time in a particular direction e.g. Velocity is a vector quantity. By vector we mean a quantity, which has both the magnitude and the direction. In metric system, the unit of velocity is same as speed-metre per second (m/s).

What is speed?

Speed is defined as the rate of change of distance moved with time e.g. Speed is a scalar quantity. By scalar, we mean a quantity, which has only magnitude but no proper direction. For example, movement of the body, movement of substances, movement of medicine, or radioisotopes through a body, all refer to some speed. In the metric system, the unit of speed is meter per second (m/s).

The acceleration of falling body is uniform acceleration.

 Freefall is a special case of motion with constant acceleration because the acceleration due to gravity is always constant and downward. This is true even when an object is thrown upward or has zero velocity. Therefore, the acceleration of a freely falling body is not absolutely uniform, it's rather constant, due to the acceleration due to gravity. 

The position of an object with respect of a point can be changed without changing its distance.

Even if the distance of a body doesn't change with respect to a point but the position of the body might change. For example, the distance with respect to the center from a body revolving in a circular path doesn't change. The value of the position vector of the body changes when the direction of the point changes. So, position changes. 

Differences between Balanced Force and Unbalanced Force

Differences between Balanced Force and Unbalanced Force. No. Balanced Force Unbalanced Force 1 The forces that act on a body and create equilibrium are called balanced force. The forces that act on a body but don't create equilibrium are called unbalanced force.  2 In this case, the resultant of the active forces is zero. In this case, the resultant of the active forces is not zero.

Why is walking hard on a muddy road?

We can easily walk on the road due to the frictional force between the road and the bottom of our feet. But the frictional force between the road and the bottom of our feet decreases in muddy roads. This is why we slip on those roads. So, it is hard to walk on muddy roads. 

Although the speed of the earth around the sun is a periodic motion but not rotational motion

 If the motion of a moving object is such that it passes repeatedly through a definite point in the same direction in the same manner in a definite interval of time, then this motion is called a periodic motion. Earth revolves around the Sun in the same direction in a parabolic path in every 1 year or 365 days, so the motion of Earth is periodic motion. Again, when a body rotates about a particular point or a line, keeping the distance of the particles of the body unchanged, it is called circular motion. Since orbit of Earth is parabolic, so the distance between Earth and Sun isn't always same, this distance is different at different times of the period. So, motion of Earth is not circular motion.

Why the motion of earth around the sun is periodic motion but is not vibratory.

When a body rotates about a particular point or a line, keeping the distance of the particles of the body unchanged, it is called circular motion. Earth revolves around sun as it crosses a specific point at specific time that is why earth's motion is circular motion.  Again, Periodic Motion If the motion of a moving object is such that it passes repeteadly through a definite point in the same direction in the same manner is called a periodic motion. However, earth revolves around sun at same direction. Therefore, it is not a periodic motion.

The differences between angiography and angioplasty.

 An angiogram is a test to find out which arteries supplying the heart have become narrowed. An angiogram uses X-rays to show 'route maps' of blood vessels and arteries in the heart. On the other hand, angioplasty is a procedure to expand narrow arteries that may follow on from an angiogram.

There is no change in acceleration without change in velocity.

 The rate of change of the non-uniform velocity of a body with time is called its acceleration. If the velocity of the body is constant that is, the body travels the same distance for every per unit time, then there will be no change in velocity. So, the velocity will be uniform velocity. Otherwise, the velocity will be non-uniform. As, acceleration depends on velocity and it has meaning only when the velocity is non-uniform, so there is no change in acceleration without a change in velocity. 

Explain how even if a bigger distance is covered displacement can be zero.

 Distance is the length covered either in a straight or curved line. And distance is the initial and final position's distance drawn in a straight line. So, if an object starts it motion and after covering a distance in a straight or curved line, but at last finishes at its initial point then the initial and final point is one and the same thus its displacement is zero.

The average velocity of a body can be zero, but average speed of a body cannot be zero.

 Speed indicates only the rate of change of position with time, it does not indicate the direction of change of position. The velocity states the rate of change of position along with its direction that is, velocity means the rate of change of position in a definite direction or in other words the rate of change of displacement. The average velocity depends on the net displacement of a body so if a body starts from a position and comes back to the same position after some time, the net displacement is zero. Consequently, the average velocity is zero. While the speed depends on the actual path length covered. It can't be zero if a body has displaced from its position. 

Explain if the falling mango supports third law

 Third law of falling bodies- The distance traversed by a freely falling body from rest in a given time is directly proportional to the square of the time.

Popular Posts

The Importance of Information and Communication Technology

রুট স্টক ও সায়ন বলতে কী বুঝ?

Programming Language Questions and Answer

When you open the gas cylinder used for cooking, which action takes place first diffusion or effusion?

ছত্রাককে মৃতজীবী বলা হয় কেন?

'দুনিয়া আখিরাতের শস্যক্ষেত্র' - ব্যাখ্যা কর।

কেন্দ্রীয় প্রবণতা (Central tendency) কাকে বলে?

কিভাবে সেচের পানির অপচয় হয়?

Information and Communication Technology

স্বাধীনতার পর যুদ্ধবিধস্ত বাংলাদেশ পূণর্গঠন প্রক্রিয়ার বর্ণনা দাও।