eBike Crackdown

[facthunter]

Jerry, Force equals Mass X Acceleration. F= M A Newtons law.   MxV is Momentum. . Nev

[old man emu]

While it is true that F= ma, what does the damage in a collision is the transfer of Momentum from one body to another.  Imagine that you  lay your open hand on a bench then slowly place a 1 kg weight on it. Because if the slow speed of the hammer as it contacts your hand, there is virtually no pain. You just feel an increase in pressure at the point of contact. Now drop the hammer from 30 cms. The hammer will have a higher velocity and therefore greater momentum. When it reaches your hand, that greater momentum is going to create more pressure (Pressure = Force per unit area) as the momentum of the hammer is transferred to your hand, and thus more pain. 

 

Also involved is the rate of change of momentum, which is called Impulse. It's the magnitude of the Impulse on your body that causes pain. If the hammer is lowered slowly, it takes longer for the transfer of momentum to take place. Therefore the Impulse is less (Impulse = Change in Momentum divided by time) than if the time taken for the hammer to transfer its momentum is less.

[willedoo]

ome, did you read that or have you tried it?

[old man emu]

Do you think that it wa a lesson hammered home to me in my youth?

 

Just thought it was the simplest way to explain the relationship between Force and Momentum that Facthunter had alluded to in his post.

 

As an aside, the reason that modern cars have crumple zones is to delay the transfer of Momentum from the initial point of contact in a collision to the bodies of the occupants who should be attached to the vehicle by restraining devices. Also the crumple zones allow for the disperal of Momentum by the deformation of the vehilce's body, the generation of sound and of heat. 

 

The Law of Conservation of Momentum, which is a special case of the Law of Conservvation of Energy, means that Momentum not transferred between colliding bodies must be changed into some other form of energy so that the total energy of the system before collision equals to total energy afterwards.

 

Random Tought:

If a bloke is subject of a Restraining Order, can he ride in vehicle unrestrained?

[willedoo]

I learnt about force and momentum and all that stuff at an early age when I went flying off the running board of the old Maple Leaf Chev, straight into a big patch of bullheads. I never did tell anyone I purposely let go to see if I could ride it round a corner without hanging on.

[willedoo]

I think it was centrifugal force I learnt that day.

[facthunter]

 Another Law of Newton. A body continues in a straight Line  at a constant speed, unless some external Impressed force acts upon it. Conservation of Momentum needs to be understood when Bodies collide. How quickly you change velocity is a Measure of the Potential for Damage ":G" load.  That's why Crumple zones work.  Nev