Chapter 5 - Using Newton's Laws

Question 1

What forces allow for circular motion to occur?

Answer 1

The centripetal force counteracts the sideways frictional force and allows for us to travel in a circular path when the radius and speed are constant.

Question 2

Is there a difference between terminal speed and velocity?

Answer 2

No they are used interchangeably but one could mean that magnitude and the other could be a vector.

Also, the max speed is the same as terminal velocity.

Question 3

How does drag differ to friction?

Answer 3

Drag is similar to friction, however it’s more about forces present when in fluids like air or water.

This is because the motion is opposed due to the collision of the fluid molecules and the object.

Question 4

Different forms of friction?

Answer 4

Static friction and kinetic friction.

Question 5

Static Friction

Answer 5

The friction of an object that is at rest.

This requires a force greater than the static friction force in order to move the object.

Question 6

Kinetic Friction

Answer 6

The friction of an object while it is in motion.

This is less than the static friction and requires less force to overcome.

Question 7

Coefficient of Friction

Answer 7

μ = Friction/Nr

Question 8

Does friction use the same forces as Newton’s 3rd law?

Answer 8

No they don’t. While the forces are equal and opposite in direction, they’re acting on the same object.

This leads to an acceleration of zero and so the person doesn’t move until static force of friction is exceeded.
(box moves or you slip)

Question 9

Why is the static frictional force <= μsNr and not like kinetic frictional force = μkNr

μ = Friction/Nr

Answer 9

Static friction can change depending on the force that’s applied. It’s only until it is exceeded where the value is then a change in motion will occur.