Download Unit V review

Physics - Unit V Review
**Considering the frictionless situation at left, understand how acceleration might
change if one or more of the features change (if mass changes, or force changes)
by filling in increases, decreases, stays the same, not enough info to tell. When
F
answering, consider Newton’s 2nd Law solved for acceleration  a =
m
1. If the mass of the cart is cut in half, the acceleration ______________________________________________
2. If the towing force is decreased to 0.25N, the acceleration _________________________________________
3. If the mass and force is decreased by half, the acceleration _________________________________________
4. If the force is applied at an angle above the horizontal, the acceleration _______________________________
5. If the track is inclined
the acceleration _____________________________________
6. If the 0.5 N force is applied to 4 carts (each 0.25kg) all connected together, the acceleration _______________
**Given a velocity vs time graph, draw the corresponding a vs t and x vs t graphs. (Unit 3 Stacks of Kinematic
Curves, or Unit 3 Kinematic Curves Quiz)
7. For the v vs t graph at right,
Section A or C, where is the net force
the smallest & why?
V
C
D
B
8. For the graph at right, is there section
where net force equals zero? Why?
A
T
©Modeling Workshop Project 2006
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Unit V review v3.0
**Determine the sum of the forces acting on an object
From dynamics information - If you are given forces, or the physical description of the system and
surroundings, draw a force diagram. Ask yourself: "Can I tell if the system is accelerating?" If yes, then the
forces do NOT add up to zero. ΣF = ma. If the system is moving at constant velocity or is motionless, then the
forces cancel out. ΣF = 0.
9. For system #1: Solve for
acceleration. μ = 0.1
the masses
are 15kg and 2 kg
10. For system #2:
Mass is 10kg, and the frictional
force is 2.5N. Draw a rotated
force diagram next to it where
the normal force is pointing up
in the positive Y-axis and the
frictional force is pointing in the
positive x-direction. What is
the value of μ?
11. For system #3: mass is 20kg, pull force is 200N, what is the acceleration?
12. For system #3: if μ = 0.1, what is the acceleration?
©Modeling Workshop Project 2006
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Unit V ws4 v3.0
Remember: break any force not on an axis into x and y components.
a) Express Fx and Fy in terms of the F. (solve for the component)
**Given kinematic information (∆x, v, t), find the acceleration first, then use
F = ma to solve for force.
a) A 12, 000 kg bus slows from 30 m/s to 10 m/s in 10 s. What is the net force acting on the bus?
b) What does a scale read for a 75 kg man in an elevator that goes from - 6.0 m/s to zero in 2.0 s ?
**Strategy
A 10 kg box is dragged across a horizontal surface ( = 0.20) by a 100 N force that is applied at a 30° angle
from the horizontal. Describe how you would go about finding the acceleration of the box. (You can solve the
problem mathematically, and then describe step by step, and why you took that step)
©Modeling Workshop Project 2006
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Unit V ws4 v3.0