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PHYS 2211 ABCDE Spring 08
MP29: Newton's Third Law
Due at 11:59pm on Thursday, February 28, 2008
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Block on an Incline Adjacent to a Wall
A wedge with an inclination of angle
rests next to a wall. A block of mass
is sliding down the plane, as shown. There is no
friction between the wedge and the block or between the wedge and the horizontal surface.
Part A
Find the magnitude,
, of the sum of all forces acting on the block.
Hint A.1
Direction of the net force on the block
Hint not displayed
Part A.2
Determine the forces acting on the block
Part not displayed
Part A.3
Find the magnitude of the force acting along the direction of motion
Consider a coordinate system with the
x
direction pointing down the incline and the
y
direction perpendicular to the incline.
In these coordinates, what is
, the component of the block's weight in the
x
direction?
Express
in terms of
,
, and
.
ANSWER:
=
"Normal," in this context, is a synonym for "perpendicular." The normal force has no component in the direction of the
block's motion (down the incline).
Express
in terms of
and
, along with any necessary constants.
ANSWER:
=
Part B
Find the magnitude,
, of the force that the wall exerts on the wedge.
Hint B.1
The force between the wall and the wedge
Hint not displayed
Part B.2
Find the normal force between the block and the wedge
What is the magnitude,
, of the normal (contact) force between the block and the wedge? (You might have computed this
already while answering Part A.)
Express
in terms of
,
, and
.
ANSWER:
=
Part B.3
Find the horizontal component of the normal force
In the previous hint you found the magnitude of the normal force between the block and the wedge. What is the magnitude,
, of the
horizontal
component of this normal force?
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MasteringPhysics: Assignment Print View
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http://session.masteringphysics.com/myct/assignmentPrint?assignmentID=1114150
Express
in terms of
and
.
ANSWER:
=
Express
in terms of
and
, along with any necessary constants.
ANSWER:
=
Your answer to Part B could be expressed as either
or
. In either form, we see that as
gets very small or as
approaches 90 degrees (
radians), the contact force between the wall and the wedge goes to
zero. This is what we should expect; in the first limit (
small), the block is accelerating very slowly, and all horizontal
forces are small. In the second limit (
about 90 degrees), the block simply falls vertically and exerts no horizontal force
on the wedge.
PSS 8.1: Dashing up the Slope
Learning Goal:
To practice ProblemSolving Strategy 8.1 for problems involving the dynamics of an interacting systems of
objects.
A girl of mass
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 Spring '08
 UZER
 Physics, Force, Assignment Print View

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