# Vocabulary

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.

$$\bf Speed = \frac{distance}{time}$$ $$expressed~as~\frac{m}{s}~or~\frac{km}{hr}$$

### Velocity

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

$$\bf Velocity = \frac{\Delta position}{\Delta time} = \frac{displacement}{\Delta time}$$ $$expressed~as~\frac{m}{s}~or~\frac{km}{hr}~along~with~a~direction$$

Δ - change in

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.

$$\bf Acceleration = \frac{\Delta velocity}{\Delta time}$$ $$expressed~as\frac{m}{s^2}$$

Δ - change in

### 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.

$$\bf Force = mass \times acceleration$$ $$expressed~as~kg\frac{m}{s^2}~or~newtons~(N)$$

### 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/s2.

### Weight

The force of gravity on an object.

$$\bf Weight = mass \times gravitational~acceleration$$ $$expressed~as~kg \frac{m}{s^2} or~newtons~(N)$$

We can demonstrate these concepts in a couple of simple sentences. 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!