Static and Kinetic Frictional Forces & Trig Funct

Question 1

component of force parallel to the surface which acts on the object
always acts in the direction to oppose motion

Answer 1

Force of friction: F(f)

Question 2

frictional force present when the surface of one object slides over the surface of another
each objects exerts this type of force on the other
sliding frictional force

Answer 2

kinetic frictional force: F(k)

Question 3

frictional force that acts even when there is no relative motion between the surfaces of two objects
makes it difficult to start a heavy box moving across a rough floor
always less than or equal to the coefficient of static friction * Normal force

Answer 3

static frictional force

Question 4

Equation: Kinetic Frictional Force

Answer 4

F(k) = (coefficient of kinetic friction) * F(n)

Question 5

Equation: Static Frictional Force

Answer 5

F(s) < or = coefficient of static friction * F(n)

Question 6

In order for an object to start moving, the force applied has to be great than the __________ * ________. I.e. In order for an object to start moving, the net force applied must overcome the force due to static friction

Answer 6

greater than F(s) = coefficient of static friction * F(n)

Question 7

Equation: Coefficient of friction

Answer 7

coefficient of friction = friction / F(n)

Question 8

Equation: Net force

Answer 8

F(net) = ∑ F(x) + ∑ F(y)

Note: Assign (-) to forces acting in opposite directions along the x or y; Force is a VECTOR–show direction

Question 9

force with which a rope or cable pulls on an object attached to it
2 necessary conditions

Answer 9

Tension: F(t)

Question 10

An object is in equilibrium when it has ____ acceleration.

Answer 10

zero acceleration

Question 11

2 necessary conditions for the force due to tension: F(t)

Answer 11

∑F(x) = 0
∑F(y) = 0

Question 12

sin(0) =

Answer 12

0

Question 13

sin(30) =

Answer 13

(1/2)

0.5

Question 14

sin(60) =

Answer 14

√(3/2)

0.86 in degrees

Question 15

sin(90) =

Answer 15

1

Question 16

cos(0) =

Answer 16

1

Question 17

cos(30) =

Answer 17

√(3/2)

0.86 in degrees

Question 18

cos(60) =

Answer 18

(1/2)

0.5

Question 19

cos(90) =

Answer 19

0

Question 20

If a picture is hanging from two ropes is at equilibrium, and the F(x) of rope 1 is 150N, what is the F(x) of rope 2? Why?

Answer 20

150 N in the opposite direction

because for Tension at equilibrium, ∑Fx = 0 and ∑Fy = 0

Question 21

Steps to solving a Tension problem at Equilibrium

Answer 21

1. Solve for the x component of the Force (tension) in Rope 1
2. Note the x component of the Force in rope 2 must = the x component of force in rope 1 but in the opposite direction (to sum to zero)
3. Set the x component of rope 2 and solve for the hypotenuse: sin(ø) = O / H

Question 22

tan(30) =

Answer 22

√(3/3)

Question 23

tan(60) =

Answer 23

√3

Question 24

sin(45) =

Answer 24

√(2/2)

Question 25

cos(45) =

Answer 25

√(2/2)

Question 26

tan(45) =

Answer 26

1

Question 27

Equation: Force on an object on an inclined plane

Answer 27

F(x) = m * g * sin(ø)

Note: Only in the absence of Friction