Download Physics 20 Dynamics – Day 15: Inclined Planes - ND

Physics 20
Dynamics – Day 15: Inclined Planes
Be able to draw a free-body diagram of an object on an incline plane and determine the
relevant forces.
In the free body diagram (FBD), all of the ______________ acting on a body are shown
(but none of their __________________ and no forces acting on other bodies). When
drawing the vectors representing the force, the vectors start with their_______ on the object
and point in the direction of the force at the ___________________________________.
The length of the vectors drawn represent their relative magnitudes.
Be able to follow through the reasoning for a complex incline plane problem.
i) Force parallel is a component of weight that ____________ the mass down the incline. It________________ as the angle increases.
ii) Force perpendicular is a component of weight that pushes the mass___________ the incline. It ___________as the angle increases.
iii)The normal force is the __________________ force of the the perpendicular force - the surface pushing on the object. It limits the
motion of the mass by creating __________________ forces.
iv) Frictional force changes from s to k when the object starts to move.
Be able to understand calculations involving inclined planes and the resolution of forces
including friction.
i) Use backwards reasoning tactics to think through the problem first.
ii) Label your diagram well so that you can remember which mass was which and what
forces acted on it.
iii) Present your solution in a formula/substitution/answer format as a sequence of steps
which is the reverse order in which you thought the problem out.
Example 1: A 2.00 kg block is located on a 35.0o inclined plane for which the coefficient of kinetic friction is 0.250. If the block is
allowed to move for 1.32 s, how far will the block move?
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S Molesky @ Notre Dame
Physics 20
Dynamics – Day 15: Inclined Planes
Example 2: A 1500 kg car is coasting down a 8.00 o icy hill where the coefficient of friction is 0.125. If the car reaches a velocity of
15.0 m/s by the bottom of the hill, how long is the hill?
Example 3: The 345 kg bicycle taxi is traveling up a 8.00 o incline at a constant velocity. If the coefficient of kinetic friction is 0.150,
what force must be exerted by the taxi driver to climb the incline?
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S Molesky @ Notre Dame
Physics 20
Dynamics – Day 15: Inclined Planes
Example 4: Mass 1, 3.00 kg, sits on a 30.0o incline which has a coefficient of friction of 0.240. A mass 2, 2.55 kg, is connected to
mass 1 by a massless rope which runs over a frictionless pulley. What is the expected acceleration of the system?
Closure:
1) What statement can be used for cases in which an object is either not moving, or moving at a constant velocity on an inclined
plane?
2) What happens to the force of friction when an object starts to move?
3) An object on an inclined plane is not moving. You give it a nudge and it continues forward at a constant velocity. How can this
happen?
4) An object is on an inclined plane and is accelerating down the incline. What can be said about the parallel force and the kinetic
force of friction?
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S Molesky @ Notre Dame