Tuesday, Dec. 10 - Motion & Work - What is Motion?

Objective: You will learn that objects are in motion all around us and that motion can be described by speed, velocity and acceleration.

An object is in motion when it is moving from one location to another.

We use several terms to describe motion:

Speed – the distance an object travels per unit of time (how fast it’s going)

Velocity – Speed plus direction in which the object is moving.

Acceleration – The rate of change of velocity.

Momentum – the product of the mass and the velocity of  a moving object.

 

Speed

Speed is the distance an object travels over a given time. It can be calculated as:

Speed= Distance / Time

It is always measured in distance and time, i.e., miles per hour.

 

Velocity

Velcocity adds direction to speed. You may know how fast something is moving, but you still can’t completely describe its motion. With velocity, you know how fast it’s moving and in what direction. “The train is moving 100 miles/hour east”

 

Acceleration

Acceleration means to go faster in our everyday world. But in physics, acceleration is the rate of change in velocity. Since velocity includes speed or direction, a change in velocity can be a change in speed or direction. A car that is slowing down is accelerating in the opposite direction of it’s motion.

A bit confusing? That’s why we call it deceleration is day-to-day life.

Acceleration = (final velocity-initial velocity) / time

If the direction in which an object is moving does not change, the change in velocity is the same as the change in speed.

 

Momentum

The larger the mass (the amount of matter in an object), the more force (push or pull exerted on and object) that is required to move it.

Basically, it’s easier to move a sandwich than a piano.

Momentum = velocity x mass

A bullet is small, but travels at high speeds, so it has a lot of momentum.

A truck is large, so even traveling slowly, it would still have a lot of momentum.

So the greater the mass, the greater the momentum. The greater the speed, the greater the momentum.

Law of Conservation of Momentum: When two objects collide, one object’s momentum can be transferred to the other object. No momentum is created or lost – as long as no other force acts on the objects.