Download Make-up #9

Name________________________
Inclined Plane WS
I. A block sits on an inclined plane whose
surface makes an angle with the horizontal.
The weight w of the block points straight down.
Complete the table.
Circle one:
w (N)

50
30
50
45
50
60
w|| = w sin

date__/__
w
w = w cos
a/ Since  can be any angle, w can be resolved into (only 2/an ∞ number of) components.
b/ If the incline is tilted up more, the angle  (decreases/increases/remains the same).
c/ As  increases, the ||-component of the weight (decreases/increases/remains the same).
d/ As  increases, the -component of the weight (decreases/increases/remains the same).
e/ As  increases, the weight (decreases/increases/remains the same).
II. No Friction.
If the incline is fricitionless, the only force causing motion along the surface is
w|| = wsinmgsinNewton’s Second Law then says:


FN
a = Fnet/ m = 
What will be the acceleration if the angle  = 300?
w||
If  equals 600?
w
If it is 900?
w
0
If it is 0 ?
Do the answers depend on the mass?
III. At Rest. If the block is at rest, the forces acting on the block are in equilibrium, so Fnet = ______ .
In the diagram at right, a 50-N block is at rest on an incline that makes an angle of 300 to the horizontal.
The weight has been resolved into w|| and w . Draw in the normal force, FN, and the frictional force, Ff.
Using w|| = from the table above, what is Ff?
Using w = from the table, what is FN?
If were increased to 450 and block remained
at rest, what would be the new value of Ff?
What would the new value of FN be?
w||
300
w
Q1. A 30.0-N block is at rest on an inclined plane whose surface makes a 240 angle to the horizontal.
a/ Find the components of the weight that are parallel (w||) and perpendicular(w ) to the surface.
w|| =
w =
b/ What are the magnitudes of the force of friction and the normal force?
Ff =
FN =
c/ If the angle were increased, what would happen…
…to Ff?
…and to FN?
Q2. A 10.0-kg crate is at rest on an inclined plane whose surface makes a 470 angle to the horizontal.
a/ Find w|| and w . Be careful! Is it the mass or the weight of the crate that is given?
w|| =
w =
b/ What are the magnitudes of the force of friction and the normal force?
Ff =
FN =
c/ If the angle were decreased, what would happen…
…to Ff?
Q3.
…and to FN?
Circle the correct answers:
As the angle of an inclined plane increases,….
…the frictional force acting on a block at rest on the incline (decreases/increases/remains the same).
…the normal force acting on a block at rest on the incline (decreases/increases/remains the same).
…the weight on a block at rest on the incline (decreases/increases/remains the same).
Q4. A 15-N block is held at rest on a frictionless incline by a string as shown
at right.
string
a/ Find the tension in the string.
b/ How would the tension change if the
incline angle were increased?
320
Q5.
A 20.0-N block is at rest on a frictionless inclined plane. The block is held in place by a string hung
over the pulley and attached to a weight.
string
pulley
block
pulley weight
350
a/ What is the tension in the string?
b/ How much does the weight weigh? (Hint: the pulley just changes the direction of the tension.)
c/ If the angle were increased, what would have to be done in order to keep the block at rest?