Physics Homework Form 2 Semester 2 2013 MJSC Baling

8/13/2019 Physics Homework Form 2 Semester 2 2013 MJSC Baling

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Acceleration

Acceleration is a way to measure how fast something is

speeding up.Some acceleration scenarios are:

1) Kicking a footballWhen a football is kicked, at first it speeds up from start (acceleration) thenagain due to friction and air resistance it slows down and finally comes torest {retardation}.

2) Throwing a ball

When a ball is thrown at a certain angle with the ground it follows sort of around path (parabolic to be exact) that means it changes direction all thetime. This is also acceleration.


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3) Braking a car

When a speeding car breaks it slows down with time. Its an accelerationexample, but some people prefer to call it retardation.

4) Pushing a pedal

When one pushes the pedal of a car it accelerates, meaning, it goes fasterwith time. It s acceleration.


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Velocity

Velocity is the rate something changes position. This can

include both speed and direction changes.Examples of velocity scenarios are :

1) Car speeding up

When a car accelerates, the engine transfers torque to the wheels and thetractional force (not frictional force because the coefficient of traction canbe greater than one) accelerates the car forward.

2) Car slowing down

In slowing down, the brakes apply a frictional force to the rotors on thetires, and the tractional force slows the car down.


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3) Turning a corner

Turning becomes more complicated, but basically the tires are turned andthe longitudinal traction is less than the lateral traction of the tire, so the car

takes the path of least resistance, and turns with the tires.

4) Sprinters racing

Instantaneous velocity is the velocity at a specific instant in time. This canbe different to the average velocity if the velocity isn't constant.

Look at the photographs of the sprinters in a race. Their velocity is different

as they take off and as they end. Their average velocity for the race doesn'tchange but their instantaneous velocity, as captured in the snapshots ofan instant in time does change. Their velocity in the photograph would bean instantaneous velocity .


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Momentum

Momentum can be defined as "mass in motion." All objects

have mass; so if an object is moving, then it has momentum -it has its mass in motion.There are two types of Momentum : Elastic and InelasticExamples of elastic momentum scenarios are:

1) Elastic momenteum

Elastic collisions are collisions in which both momentum and kinetic energyare conserved. In the collision between the truck and the car, total systemmomentum is conserved.Before the collision, the momentum of the truck is 60000 kg*m/s and themomentum of the car is 0 kg*m/s; the total system momentum is 60000kg*m/s.After the collision, the momentum of the truck is 30000 kg*m/s and themomentum of the car is 30000 kg*m/s; the total system momentum is60000 kg*m/s.The total system momentum is conserved.


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2) Inelastic momentum

If total kinetic energy is not conserved, then the collision is referred to as aninelastic collision.In the collision between a truck and a car, total system momentum is

conserved.Before the collision, the momentum of the truck is 60000 kg*m/s and themomentum of the car is 0 kg*m/s; the total system momentum is 60000kg*m/s.After the collision, the momentum of the truck is 45000 kg*m/s and the

momentum of the car is 15000 kg*m/s; the total system momentum is

60000 kg*m/s.The total system momentum is conserved.The momentum lost by the truck (15000 kg*m/s) is gained by the car.


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Inertia

The term " inertia " refers to the tendency of matter to

continue to move, or to stay at rest, unless an external forceacts upon it.Some inertia scenarios are:

1) Movement of brain after an impactA football player is tackled and his head hits the ground. The impact stopshis skull, but his brain continues to move and hit the inside of his skull. Hisbrain is showing inertia .

2) Illusion of body moving backwards as vehicles accelerate

When a car is abruptly accelerated, drivers and passengers may feel asthough their bodies are moving backward. In reality, inertia is making thebody want to stay in place as the car moves forward.
http://www.yourdictionary.com/inertiahttp://www.yourdictionary.com/inertia


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3) Pulling a tablecloth under dishes

If pulled quickly, a tablecloth can be removed from underneath dishes. Thedishes have the tendency to remain still as long as the friction from the

movement of the tablecloth is not too great.

4) Continuance of hockey puck

A hockey puck will continue to slide across ice until acted upon by an outsideforce.


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Speed

Speed is a measurement of how fast an object moves relative

to a reference point. It does not have a direction and isconsidered a magnitude or scalar quantity. Some speed scenarios are:

1) A moving car

If a car is traveling at the rate of 100 miles per hour the speed can be

determined by how far it has traveled since it started moving.

2) Running a marathon The speed can be measured by calculating theaverage distance and average time.


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Physics Homework Form 2 Semester 2 2013 MJSC Baling

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