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Several problems related to free-body diagrams and potential energy. The scenarios include a car rounding a banked curve, a rider in a barrel of fun, a pogo stick rider, a projectile in motion, a constant force spring, a planet in elliptical orbit, and a pendulum launched in two different ways. Questions ask about the correct y-equation for a car, the relationship between normal force and weight for a rider, the maximum potential and kinetic energy points for a pogo stick, the work done by forces during projectile motion, the potential energy of a constant force spring, the comparison of potential and kinetic energy for a planet, and the escape velocity of a rock. The typology of this document is 'problems' or 'exercises'.
Typology: Exams
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RII-1.
The free-body diagram for a car rounding a banked curve is shown. The car
is going so fast that it is about to slip. The coordinate system has been
chosen.
What is the correct Y-equation:
A: N sin + sN cos – mg = 0
B: N – sN sin – mg cos = 0
C: N – mg cos = 0
D: N cos – sN sin – mg = 0
E: None of these.
a
mg
s
N
N
y
x
RII-3. A rider in a "barrel of fun" finds herself stuck with her back to the
wall. The free-body diagram is shown.
Is the following statement definitely true for this situation?
sN=mg
A: Yes, it is certainly true. B: No, it might not be true.
RII-5. A projectile is fired straight up and then it comes back
down to its original height. There is air resistance as the projectile
is moving. During the flight of the projectile, the work done by the
force of gravity is..
A: zero. B: positive D: negative
During the flight of the projectile, the work done by the force of air
resistance is...
A: zero. B: positive C: negative
RII-6. A new "constant force spring" is invented which has the
remarkable property that the force exerted by the spring is
independent of the stretch of the spring, Fspr = –q, where q is a
constant. What is the potential energy contained in this spring
when it is stretched a length x.
A: (1/2)qx
2
B: q x C: q
D: None of these.
The gravitational potential energy of a rock near a star is shown in
the diagram. When the rock is at the position shown, it has a
kinetic energy of 25MJ. Will the rock escape to infinity or is it
bound in orbit about the star?
A: Escape B: in bound orbit
C: impossible to tell
U(r)
r
0
CTRII-9. A pendulum is launched in two different ways. During
both launches, the bob is given an initial speed of 3.0 m/s and the
same initial angle from the vertical. On launch 1, the speed is
upwards, on launch 2, the speed is downwards.
Which launch will cause the pendulum to swing the largest angle
from the equilibrium position on the left side?
A: Launch 1 B: Launch 2
C: Both launches give the same maximum displacement.
1
2
