MY OBSERVATIONS WHEN DROPPING THE CLICK PART OF A CLICK PEN ONTO A BOOK.

[Marcus]

Hi everyone, just as a quick introduction I am an I.T. graduate and only did physics in high school. I wrote the following 4 years into my I.T. studies and I am posting it up because I want to get an honest rating from 'science people'. So please give it a look and a rating.

 

THE FOLLOWING ARE MY OBSERVATIONS WHEN DROPPING THE CLICK PART OF A CLICK PEN ONTO A BOOK. THE CLICK END PRESSED IN THE HIGHER THE PEN WAS DROPPED ONTO THE BOOK. NOTHING HAPPENED TO THE BOOK

The velocity of an object with constant mass freefalling does not change because of gravity accelerating at a constant speed(9.8m/s).

It seems as though the height from which that object falls determines the amount of force with which it hits the book.

The higher the height from which the pen falls the more force it exerts on the book (Someone can easily try and jump off a 1 meter high wall and land safely but jumping off a 3 meter high wall will surely result in some injury to that someone).

How is this if the objects velocity remains constant?

This possibility comes from momentum.

[This is my understanding of momentum:]

Momentum = the amount of speed you pick up the longer you are in motion.

So when running down a steep gradient you will start to accelerate and at some point after that you will try and come to a stop but the momentum you have picked up will resist this change and makes it hard for you to stop.

The objects momentum increases the longer it falls which means the higher the height from which it falls the more the momentum.

m∆ [1]

Therefore: m∆ = s(distance)*velocity [2]

The momentum has an effect on the force with which the object hits the ground:

F = m∆ * g-1 [3]

Or

F = m∆ * mass

 

But is gravity not a constant ACCELERATION?

Does gravity itself accelerate at a constant speed or does it cause an object to accelerate at that rate?

Gravity’s acceleration increases the objects speed.

Therefore force is proportional to change in momentum : F = m∆.

As momentum increases the force exerted on a surface will increase.

This brings me to the main focus of the observation .

Newton’s 3rd law says “When an object exerts a certain force on another, the other object exerts an equal force on it in the opposite direction”.

But when one object collides with another (in this case a small object falling onto a book) the resultant effect on one can be more visible than on the other.

From this I deduce that it comes down to mass.

The object composed of more mass will have more of an effect on the object composed of less mass.

The following are footnotes

1: change in momentum

2: I don’t remember physics formulas that well but I think this one is known.

3: Gravitational speed = 9.8m/s-1. Let me just highlight that this and the next formula are my understanding but to be real, they probably don’t exist. At the same time I am aware that one cannot just come up with scientific formulas and that you have to show by means of calculations how you got to the solution. Time and limited knowledge of physical science did not allow me to do that.

[DrP]

The velocity DOES change.... The higher - the more force due to greater velocity... The constant ACCELERATION means it is getting faster constantly with the force on it... (until it reaches terminal velocity... which it won't dropped a few feet above your book). Thus the pen dropped from higher up hits the book with more force, as per your observations.

 

Hope this helps.

 

 

KE = 1/2 M V^2 might help also... the faster the pen, the more energy.

[Nicholas Kang]

The velocity of an object with constant mass freefalling does not change because of gravity accelerating at a constant speed(9.8m/s).

 

Acceleration means change in velocity.

Velocity means Speed of an object together with its direction of movement-thus is is a vector quantity, unlike speed which is a scalar quantity without considering its direction.

 

If I say a car travelling 60km/h. Its speed is 60km/h. The velocity is unable to be determined since the direction of motion is not given. But if I add a direction statement like 60km/h eastward. Then the velocity is 60km/h in the direction of east.

 

Acceleration can therefore either be change in speed or change in direction.

The velocity of an object with constant mass does change in free fall in Earth`s Gravitational Field since gravitational acceleration cause the object to accelerate, which means the velocity of the object would increase by 9.8m/s every second, for simple calculation, usually it is round off to 10m/s.

 

If it drops at first second, the speed is 0m/s, after 1 second it is 10m/s, after 2 second it is 20m/s and so on. (Assuming gravitational constant is 19m/s²)

 

It seems as though the height from which that object falls determines the amount of force with which it hits the book.

The higher the height from which the pen falls the more force it exerts on the book (Someone can easily try and jump off a 1 meter high wall and land safely but jumping off a 3 meter high wall will surely result in some injury to that someone).

 

This has something to do with momentum(but not in all aspects). Momentum = mass times velocity

 

The height does indirectly affect the result. Since the higher the object from the ground, the longer the time available for the object to gain velocity. So, the higher the object is from the ground, the larger the magnitude of the final velocity when it touches ground. So, the larger the value for velocity. A large value of velocity times mass will give you a larger momentum, thus the greater the impact.

 

To calculate the change in momentum, we can use Newton`s Second Law of Motion written in the "acceleration" version. Another version is the "mass" version.

 

The acceleration version: F= (mv/mu)/t-----(1)

The mass version: F=ma-----(2)

 

We use the acceleration version in this context. Rearranging (1), we get Ft=mv-mu

Ft=mv-mu. This product is known as impulsive force or change in momentum.

 

Refer: http://fiziknota.blogspot.com/2009/05/impulse-and-impulsive-force.html

(A Malaysian Form 4 16 years old Physics Syllabus Website)

 

 

[imatfaal]

Nicholas - you have a typo in your equation number (1)