# Vocabulary

## Zip Line Concepts in Action

We can describe the action of riding a zip line using the scientific terms that are defined below in a couple of simple sentences: When you step off the platform to begin your zip ride, the**force**of

**gravity**pulls your

**mass**down the zip line. You will

**accelerate**until you reach your maximum

**velocity**. If it wasn't for air resistance along with the opposing

**force**created by

**friction**, you could have gone even faster!

Want to calculate your zip line speed and maximize your adventure? We need to know the definitions of eight (8) keywords so as to understand the science of riding a zip line.

### Speed

The distance traveled over a specific period of time.

*$\mathrm{Speed}=\frac{\mathrm{distance}}{\mathrm{time}}\phantom{\rule{0ex}{0ex}}\mathrm{expressed}\mathrm{as}\frac{m}{s}or\frac{\mathrm{km}}{\mathrm{hr}}$*

### Velocity

The speed of an object in a given direction. Velocity is a vector quantity, having both a specified speed and direction.

*$\mathrm{Velocity}=\frac{\mathrm{\Delta position}}{\mathrm{\Delta times}}=\frac{\mathrm{displacement}}{\mathrm{\Delta time}}\phantom{\rule{0ex}{0ex}}\mathbf{\text{\Delta -changein}}\phantom{\rule{0ex}{0ex}}\mathrm{expressed}\mathrm{as}\frac{m}{s}\mathrm{or}\frac{\mathrm{km}}{\mathrm{hr}}\mathrm{along}\mathrm{with}a\mathrm{direction}$*

In practice, the terms velocity and speed are used interchangeably.

### Acceleration

The rate at which velocity changes, or the change in velocity per unit of time. Acceleration can result from a change in speed, a change in direction, or a combination of changes in speed and direction.

*$\mathrm{Acceleration}=\frac{\mathrm{\Delta velocity}}{\mathrm{\Delta time}}\phantom{\rule{0ex}{0ex}}\mathbf{\text{\Delta -changein}}\phantom{\rule{0ex}{0ex}}\mathrm{expressed}\mathrm{as}\frac{m}{{s}^{2}}$*

### Mass

The amount of matter in an object, expressed in grams (g) or kilograms (kg). Every physical object has mass, and this mass is constant no matter where the object may be (Earth, Saturn, Jupiter , or any other location).

### Force

Usually a push (repulsive force) or pull (attractive force) that causes a change in the movement or geometrical shape of a freely moving object. Force is a vector quantity meaning that it has both magnitude and direction.

*$\mathrm{Force}=\mathrm{mass}\times \mathrm{acceleration}\phantom{\rule{0ex}{0ex}}\mathrm{expressed}\mathrm{as}\mathrm{kg}\frac{m}{{s}^{2}}\mathrm{or}\mathrm{newtons}\left(N\right)$*

### Friction

The force two touching objects exert on each other that resists motion between them. The force of friction is always in the opposite direction of the motion of an object across the surface.

### Gravitational Acceleration

The acceleration of an object caused by the force of gravity - a force that attracts
two objects towards each other due to their mass. On Earth, gravitational acceleration
is a constant that is equal to 9.81 m/s
^{2}.

### Weight

The force of gravity on an object.

*$\mathrm{Weight}=\mathrm{mass}\times \mathrm{gravitational}\mathrm{acceleration}\phantom{\rule{0ex}{0ex}}\mathrm{expressed}\mathrm{as}\mathrm{kg}\frac{m}{{s}^{2}}\mathrm{or}\mathrm{newtons}\left(N\right)$*