Topic 10 friction and drag HL

Question 1

What is friction

Answer 1

Friction occurs when two surfaces are in contact and acts opposite to relative motion

Question 2

What is the relationship between coefficient of friction and friction

Answer 2

The higher the coefficient of friction the more friction there is. (Skates on ice have lower coefficient of friction than studs on football pitch)

Question 3

Define coefficient of friction and what it depends on?

Answer 3

Coefficient of friction is the ration of the friction between two surfaces. It’s affected by the material in contact.

Question 4

Standard deviation

Answer 4

Shows the spread/variation of results around the mean

Question 5

explain how a gymnast will manipulate their moment of inertia when doing a flip (3)

Answer 5

-High moment of inertia = low angular velocity
-gymnast tuck in - lower moment of inertia - increases angularvelocity
- before landing - gymnasts tucks outwards - slowing the rotation and increasing moment of inertia

Question 6

Explain the differences between static and dynamic friction (3)

Answer 6

static: maximum possible of frictional force before an object moves
dynamic: ammount of force required to overcome static friction, causing movement
More force is required to overcome static friction and dynamic

Question 7

Newton’s first law

Answer 7

An object will remain at rest unless acted by an external force

Question 8

bernouli’s law (5)

Answer 8

• Bernouli’s law explains how relative air pressure around a ball means that it will experience a lift force and travle further
• the (back) spin of a projectile means that it will experience low pressure at the top and high pressure at bottom
• ball is attracted to area of low pressure, top of the ball, will experience lift
• lift is perpendicular to airflow
• faster the ball travels greater the lift

Question 9

Types of drag and how they can be reduced in swimming

Answer 9

Surface drag: The outer surface catches a layer of fluid
Swimsuit (more smooth)
form drag: reaction of a fluid when body pushes against it
improve technique/form
wave drag: displacement of fluid as a body moves through its surface
swimming underwater

Question 10

drag

Answer 10

force acting opposite of the motion of an object through a fluid