Chapter 3 - Friction

Question 1

State the equation for friction force

Answer 1

F = coefficient of friction (u) x N (normal force to the resting surface

Question 2

State the equation for static friction, not moving

Answer 2

Us = tan a

where a is the angle where object begins to move

Question 3

State the equation for centripetal force

Answer 3

Fc = mV^2/r

Question 4

State two rules regarding the normal force

Answer 4

The normal force must always point upwards
The normal force must always be perpendicular to the plane

*when you double the distance, you quarter the force

Question 5

In circular motion what direction are velocity and the centripetal acceleration?

Answer 5

The velocity is tangential to the circle (outwards)

whilst centripetal acceleration is directed towards the centre

Question 6

State the equation for constant circular motion

Answer 6

V^2/r

Question 7

State the equation for the gravity force perpendicular t the surface

Answer 7

mg cos theta = perpendicular to the surface

Question 8

State the equation for the gravity force parallel to the surface, down the incline

Answer 8

mg sin theta = parallel to surface, down the incline

Question 9

What is the acceleration if the constant velocity is 10m/s and the radius is 50m?

Answer 9

ac = v^2/r = 10^2/50 = 2m/s