Ch6_1
New Problems
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Make sure to calculate your answers in SI units unless specified otherwise .
1) A box on a frictionless horizontal plane is pulled a distance of
m
by an attached rope which makes an
degrees
angle with the vertical and is under a
N
tension. What is the work done
(see sheet 3)
. Indicate with a negative (positive) sign whether the component of the tension perpendicular to the displacement is doing work (does not do any work).
2) An object with a
kg
mass is lifted by a force acting vertically upward a distance of
m
. During the lift the object rises with constant speed. What is the work done by the upward force
(see sheet 5)
? Indicate with a negative (positive) sign whether the work done by the net force is zero (is not zero).
3) A horizontal force of
N
pushes a
kg
block which is initially at rest on a horizontal frictionless plane for a distance of
m
. What is the final velocity of the block
(see sheet 3,8,9)
? Indicate with a negative (positive) sign whether you can (cannot) arrive at the same result using Newton's Law II and the expression
(2.7) from Ch 2
, that is by not using any energy principle.
4) A
kg
box, initially on a table, is lifted a height of
m
. What is the change in potential energy
(see sheet 12-14)
? Indicate with a positive (negative) sign whether the box at its final height has the same (different) potential energies relative to the floor and the table top.
5) A person starting with an initial downward velocity of
m/s
falls a vertical distance of
m
. What is the final velocity of the person
(see sheet 15)
? Neglect friction in the air and indicate with a negative (positive) sign whether your equation for the conservation of the mechanical energy leads (does not lead) to equation
(2.7) in
Ch 2
, that is an equation which does not use any energy principle.
6) A roller coaster, initially at rest, starts from
m
above ground, travels down into a valley
m
below the start point, rises back up a height of
meters
and descends from there to the ground. With what speed does it arrive at the bottom
(see sheet 16-18)
? Neglect any friction and indicate with a positive (negative) sign whether the roller coaster after having fallen from the initial height straight down to the ground would have arrived with the same (a different) speed as calculated at the bottom
(
assuming no friction,
see sheet 18')
.
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cannot resubmit answers
for the same Problem Set--you must use the 'New Problems' button first.