Physics Practical Report Momentum PDF

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By Andrew Park

Physics Practical Report- Momentum in one and two dimensions Outcomes Inquiry Question- How is the motion of objects in a simple system dependent on the interaction between objects? Working Scientifically -

Conduct an investigation to describe and analyse one-dimensional (collinear) and two-dimensional interactions of objects in simple closed systems Evaluate the effects of forces involved in collisions and other interactions, and analyse quantitively the interactions using the concepts of impulse Analyse and compare the momentum and kinetic energy of elastic and inelastic collisions

Aim To explore what happens to the momentum of a trolley (physics) in a collision?

Risk Assessment Identify Trip hazard of the trolley placed on the ground Spring of trolley may hit face Getting hit by trolley

Rating Mediu m Low Low

Minimisation Make sure to pack away trolleys, keep a distance and be aware of where they are placed Compress spring pointing to the ground, away from face Clear area of collision and be aware of where experiment is being conducted

Equipment -

Two physics trolleys Walls (top side of tables) 30cm and 1m ruler

Procedure 1) 2) 3) 4) 5) 6) 7) 8)

Get two physics trolleys and cover Velcro with sticky tape Find clear area to conduct experiment Set up the trolleys in the three everyday traffic collisions For all three scenarios, ensure one has a spring Push spring into the second notch, past the first notch then push up to lock in Push button to release spring Push the spring off a wall Place the cars no greater than 30cm apart

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9) Rear to end collision 10) Place cars in a linear way Wall

Trolley 1

Trolley 2

11) T-Bone 12) Turn one car to get hit in a turned away 13) Place 30cm away Wall

Trolley 2

Trolley 1

14) Head on 15) Ensure both trolleys have a spring attached to the back 16) Place 30cm apart 17) Push the springs in on both trolleys 18) Place both trolleys against walls 19) Push the buttons of the trolleys at the same time

Wall

Trolley 1

Trolley 2

Wall

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20) Record observations after the collision for each scenario

Results Table Rear to end

T-Bone

Head on

Rear to end

T-Bone

Head on

Before collision Trolley 1 Trolley 2 Trolley 2 remains stationary, linear to After the push, the trolley trolley 1 until trolley 1 collides with it accelerates with a push of speed in a linear direction towards trolley 2 Trolley 1 Trolley 2 Trolley 1 accelerates after pushing Trolley 2 remains stationary in a off the wall in a linear direction perpendicular direction from trolley 1 towards trolley 2 until trolley 1 collides with it Trolley 1

Trolley 2

Trolley 1 accelerates after pushing off the wall, towards trolley 2

Trolley 2 also pushes off its own wall in the direction of the other trolley, travelling at the same time

Observation of trolleys after collision The momentum exerted by trolley 1 is transferred to trolley 2, causing it to accelerate. After the collision, trolley 1 slows down and trolley 2 starts to move. The mass of the experiment is in the same direction in a linear way. The same amount of momentum is transferred, however trolley 2 does not move as much as the wheels are in a 90 degree (perpendicular) direction to the momentum If forces are equal, the objects will be displaced. When one is pushed back from the other, one has more momentum than the other. Both trolleys rebound off each other and are projected back towards the walls

Analysis 1) Explain why trolleys change velocity and or direction when they collide In a collision between the trolleys, they affect each other in a way that changes their direction and speed of travel after. Trolley 1 initially has momentum whereas trolley 2 does not. Trolley 1 transfers momentum into the 2nd trolley causing it to accelerate. Trolley 1 slows down and eventually stops, then trolley 2 starts to move. As it is linear, the trolleys move in the same direction. As energy cannot be destroyed, the momentum is lost from trolley 1 and momentum is gained in trolley 2.

By Andrew Park

2) Using Newton’s 2nd law describe the affect of force acting on trolleys in a collision Newton’s second law states that the acceleration of the trolley is proportional to the force. The force exerted by both trolleys and are measured through the mass multiplied by the acceleration. In the two scenarios where one trolley is stationary, that trolley exerts zero force as the mass is multiplied by zero. Then, the force exerted by the trolley that is accelerating, transfers momentum onto the stationary trolley causing it to accelerate. For the head on collision, both trolleys exert the same force if both trolleys accelerate at the same time. 3) Define one and two dimensional collisions One dimensional is when both objects are facing the same direction, face to rear. Two dimensional is when one is travelling horizontal (x-axis) and one is travelling across the plane (y-axis).

Conclusion 1) Definition of momentum, formula, units Momentum is a property an object has because of its motion and is a similar concept to inertia. Linear momentum is a product of an object’s mass and its velocity (p=mv). Units are: Kg.m.s/-1 or N.s. Momentum is a vector and the direction of momentum = direction of velocity. The more momentum an object has, the harder it is to stop it and the greater effect it will have if it is brought to rest by impact or collision. Force is required to change the momentum of an object (increase or decrease or change direction). 2) Describe the law of conservation of momentum, formula The law of conservation of momentum is momentum cannot be created or destroyed but only transferred or transformed. Net potential before = Net potential after. For onedimensional problems, we us + or – to show direction. For two-dimensional problems, we must add the momentum vectors graphically or resolve the momentum vectors into components at right angles to each other, process these as one-dimensional problems and then combine the two components using Pythagoras and trigonometry.

By Andrew Park

Extension From our understanding now of collisions, discuss how 4WD and trucks affect cars in an accident A motor vehicle collision is when a vehicle collides with another vehicle, pedestrian or a stationary obstruction. The major factor that contributes to the severity of a collision is vehicle design and speed of operation. In a collision that includes of a 4WD and trucks with a car, there is a much greater collision force than a car and another car. This is due to the sturdy and larger structure and higher mass that is within both a 4WD and truck compared to a car. Due to this difference in size, the force exerted by the larger car causes an impact on the smaller car. Newton’s second law states that the net external force of an object is dependent on the mass multiplied with the acceleration. This proves that the force exerted by the larger vehicle will be much greater than the force exerted by the smaller force, resulting in the smaller car receiving more damage from the collision. In addition, after the impact, the larger vehicle will cause the smaller vehicle to accelerate opposite its direction.

Crumple Zones Crumple zones are areas of a vehicle that are designed to deform and crumple in a collision and are also one of the most effective innovations in auto safety. They are designed to absorb the energy from the impact during a crash through controlled deformation by crumpling. This device helps passengers in a collision as the energy is absorbed through crumpling, preventing it from being transmitted to the occupants. The crumple zones are typically located in the front part of the vehicle to absorb the impacts of a head-on collision as they are the most dangerous, crumple zones can also be found in other parts of the vehicle. Crumple zones work through managing crash energy by absorbing energy with the outer parts of the vehicle. This is achieved by controlled weakening of certain areas of the outer parts of the car while strengthening and increasing the rigidity of the inner part of the car, making the passenger cabin a safety cell. When energy reaches the safety cell, it is spread over as wide an area possible, reducing deformation. Designers must balance between too much impact resistance and too little impact resistance. This can be done through using simple designs such as frame segments that can bend or collapse. Also by using more advanced designs such as using a variety of metals and other materials engineered to absorb as much kinetic energy as possible or using a honeycomb design.

By Andrew Park

Web Accessed https://en.wikipedia.org/wiki/Crumple_zone https://auto.howstuffworks.com/car-drivingsafety/safety-regulatory-devices/crumplezone.htm https://en.wikipedia.org/wiki/Traffic_collision https://en.wikipedia.org/wiki/Truck

Name of Organisation Wikipedia howstuffworks

Date Accessed 20/4/2019 20/4/2019

Wikipedia Wikipedia

21/4/2019 21/4/2019...