One easy way to reduce heating (and cooling) costs is to add extra insulation in the attic of a house. Suppose the house already had 15 cm of fiberglass insulation in the attic and in all the exterior surfaces. If you added an extra 8.0 cm of fiberglass to the attic, then by what percentage would the heating cost of the house drop? Take the single story house to be of dimensions 10 m by 15 m by 3.0 m. Ignore air infiltration and heat loss through windows and doors.
One easy way to reduce heating (and cooling) costs is to add extra insulation in the attic of a house. Suppose the house already had 15 cm of fiberglass insulation in the attic and in all the exterior surfaces. If you added an extra 8.0 cm of fiberglass to the attic, then by what percentage would the heating cost of the house drop? Take the single story house to be of dimensions 10 m by 15 m by 3.0 m. Ignore air infiltration and heat loss through windows and doors.
One easy way to reduce heating (and cooling) costs is to add extra insulation in the attic of a house. Suppose the house already had 15 cm of fiberglass insulation in the attic and in all the exterior surfaces. If you added an extra 8.0 cm of fiberglass to the attic, then by what percentage would the heating cost of the house drop? Take the single story house to be of dimensions 10 m by 15 m by 3.0 m. Ignore air infiltration and heat loss through windows and doors.
A 10-m-long glider with a mass of 680 kg (including the passengers) is gliding horizontally through the air at 28 m/s when a 60 kg skydiver drops out by releasing his grip on the glider. What is the glider's speed just after the skydiver lets go?
PROBLEM 2
A cube of mass m is placed in a rotating funnel.
(The funnel is rotating around the vertical axis shown
in the diagram.) There is no friction between the cube
and the funnel but the funnel is rotating at just the
right speed needed to keep the cube rotating with the
funnel. The cube travels in a circular path of radius r,
and the angle between the vertical and the wall of the
funnel is 0. Express your answers to parts (b) and (c)
in terms of m, r, g, and/or 0.
(a) Sketch a free-body diagram for the cube. Show
all the forces acting on it, and show the appropriate
coordinate system to use for this problem.
(b) What is the normal force acting on the cube?
FN=mg58
(c) What is the speed v of the cube?
(d) If the speed of the cube is different from what you
determined in part (c), a force of friction is necessary
to keep the cube from slipping in the funnel. If the
funnel is rotating slower than it was above, draw a
new free-body diagram for the cube to show which
way friction…
Circular turns of radius r in a race track are often banked at an angle θ to allow the cars to achieve higher speeds around the turns. Assume friction is not present.
Write an expression for the tan(θ) of a car going around the banked turn in terms of the car's speed v, the radius of the turn r, and g so that the car will not move up or down the incline of the turn.
tan(θ) =
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