Physics - 9203 OxfordAQA

Momentum P

Gbogbo ọrọ náà

A bullet leaves a rifle at four hundred metres per second and a cricket ball leaves a bat at thirty. Which one is harder to stop? The honest answer is the cricket ball, and the quantity that says so is momentum. Speed on its own tells you almost nothing about how much effort an object will cost you to bring to rest. Mass on its own tells you almost nothing either. Multiply them together and you have the single number that governs every collision, every recoil and every crash on the planet.

This lesson builds that number from scratch and then uses it. You will learn to treat momentum as a directed quantity with a sign rather than a bare figure, apply the one law that lets you predict the outcome of a collision you have never seen, and finish with the equation that explains why a gymnast lands on a thick foam mat and a cricketer draws the hands back to take a catch. It is one of the few topics in the whole course where three short equations let you answer questions that look, at first sight, impossible.

Ebumnobi

All moving objects have momentum. The relationship between momentum, p, mass, m, and velocity, v, is: p = m×v
In a closed system the total momentum before an interaction is equal to the total momentum after the interaction. This is called conservation of momentum. Students may be required to complete calculations involving two objects. Examples of interactions are collisions and explosions.
The relationship between force, F, change in momentum, ∆p, and time, t, is: F = ∆p / t ie the force equals the rate of change of momentum. Students should be able to use this relationship to explain qualitatively car safety features such as air bags, seat belts, side impact bars, crumple zones. Also, gymnasium crash mats, cushioned surfaces for playgrounds and cycle helmets.

Maapụ uche

E seela isiokwu a ka ị hụ otu echiche si ejikọta.

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Akwụkwọ Ọmụmụ

Put a wooden board in front of a rifle bullet travelling at 400 metres per second and the board will not stop it. Put the same board in front of a cricket ball at 30 metres per second and it probably will. That looks like a verdict on speed, and it is not. The bullet has a mass of about ten grams; the cricket ball has sixteen times as much. Work out mass multiplied by velocity for each and the bullet comes out at 4.0 kg m/s while the ball comes out at 4.8 kg m/s. The ball actually carries the larger quantity of motion. What defeats the board is not the bullet's motion but the tiny area it is concentrated into and the very short time the impact lasts, and by the end of this lesson you will be able to say exactly why that matters.

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Nnyocha Ọmụmụ

Ekele diri gi maka imecha ihe karịrị na Momentum P. Ugbu a na ị na-enyochakwa isi echiche na echiche ndị dị mkpa, ọ bụ oge iji nwalee ihe ị ma. Ngwa a na-enye ụdị ajụjụ ọmụmụ dị iche iche emebere iji kwado nghọta gị wee nyere gị aka ịmata otú ị ghọtara ihe ndị a kụziri.

Ị ga-ahụ ngwakọta nke ụdị ajụjụ dị iche iche, gụnyere ajụjụ chọrọ ịhọrọ otu n’ime ọtụtụ azịza, ajụjụ chọrọ mkpirisi azịza, na ajụjụ ede ede. A na-arụpụta ajụjụ ọ bụla nke ọma iji nwalee akụkụ dị iche iche nke ihe ọmụma gị na nkà nke ịtụgharị uche.

Jiri akụkụ a nke nyocha ka ohere iji kụziere ihe ị matara banyere isiokwu ahụ ma chọpụta ebe ọ bụla ị nwere ike ịchọ ọmụmụ ihe ọzọ. Ekwela ka nsogbu ọ bụla ị na-eche ihu mee ka ị daa mba; kama, lee ha anya dị ka ohere maka ịzụlite onwe gị na imeziwanye.

What is the unit of momentum? A. N B. J C. kg m/s D. m/s Answer: C
Which pair of quantities are both vectors? A. Mass and speed B. Momentum and velocity C. Distance and time D. Energy and mass Answer: B
A trolley of mass 4.0 kg moves at 2.5 m/s. What is its momentum? A. 1.6 kg m/s B. 6.5 kg m/s C. 10 kg m/s D. 20 kg m/s Answer: C
Two identical carts roll towards each other at the same speed and stick together on impact. What is the total momentum of the pair immediately after the collision? A. Zero B. Twice the momentum of one cart before the collision C. The same as the momentum of one cart before the collision D. Greater than it was before the collision Answer: A
A car is brought to rest in a collision. The change in momentum is the same, but the car is designed so that the collision lasts longer. What happens to the average force on the car? A. It increases B. It decreases C. It stays the same D. It becomes zero Answer: B

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