Drag and Terminal Velocity

Fluid

A substance that can flow

Which states are fluids

Liquids and gases

Drag

Friction in a fluid

State a type of drag

Air resistance

What is drag also called

Fluid resistance

What does drag depend on

-Viscosity of fluid

-Speed of object through fluid

-Shape of object through fluid

If viscosity increases, what happens to drag

Increases

If speed of the object moving through the fluid increases, what happens to the drag

Increases

If the shape of the object moving through the fluid has a larger surface area, state what happens to the drag

Increases

If air resistance is ignored for a projectile’s distance travelled, will the true calculation be an overestimate, or underestimate

Overestimate

Which direction do frictional forces act

In the opposite direction to the motion of the object

Explain whether frictional forces can cause acceleration

They cannot, they always act against movement, so if there is no movement there can be no frictional forces

Energy conversions of frictional forces

Convert kinetic energy into heat and sound

Terminal Velocity

When frictional forces equal the driving force and the object moves at a constant velocity

Explain how terminal velocity is reached

A driving force is applied, causing it to accelerate from rest. As velocity increases, frictional forces increase, reducing the resultant force until there is none. With no resultant force, the car no longer accelerates due to Newton’s 2nd Law and moves with a constant velocity

What is needed for a terminal velocity to be reached

-A constant driving force

-A frictional force, increasing with velocity

Ways of increasing a vehicle’s terminal velocity

-Increasing driving force

-Reducing frictional force

How to increase the driving force

Increase engine size

How to reduce frictional forces

Make the body more streamlined

Explain how a skydiver reaches terminal velocity

When a skydiver leaves the plane, his weight accelerates him downwards, increasing his velocity, which increases air resistance, reducing resultant force until there is no acceleration

Why can’t a skydiver land from free fall

The terminal velocity is too high

Explain how a skydiver can survive a free fall

Before reaching the ground, he opens his parachute. This increases air resistance, making it bigger than his weight, causing him to decelerate, lowering his velocity and air resistance, until it equals his weight again, reaching a new, lower, terminal velocity