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10. A pulley system operated with an electric motor consumes 5.0 kJ of energy as it does 3.2 kJ of work in raising an object. The efficiency of this technology is:
(a) 64% (b) 84%
(c) 119% (d) 156%
8. Consider an object falling from a height of 300 m. If we ignore air resistance, its total energy:
(a) increases during the fall.
(b) decreases during the fall.
(c) remains constant during the fall.
(d) is zero at the start of the fall.
7. In which of the following is gravitational potential energy being transformed into kinetic energy?
(a) A car accelerating on a level road.
(b) A raindrop falling freely through the air.
(c) Water turning an electric turbine.
(d) A stone thrown up into the air.
6. If the mass of an object is quadrupled and the speed decreased by a factor of three, by what factor does the kinetic energy change?
(a) 4/3 (b) 16/3
(c) 4/9 (d) 16/9
9. A 6.0 kg object (at rest) is released from a height of 80 m. If air resistance is negligible and g = 9.8 N/kg, the kinetic energy of the mass when it is 20 m above the ground is:
(a) 4.7 × 103 J (b) 3.5 × 103 J
(c) 2.4 × 103 J (d) 1.2 × 103 J
Cody car accelerates from 0m/s to 45m/s northward in 15 seconds. What is the acceleration of the car?
A 2 kg rectangular thin plate has a length of 0.5 m and a width of 0.20. the moment of inertia
of the plate is 0.29 kg-m2
. Where is the location of the axis of rotation?
a uniform sphere has a radius of 0.10 m. the moment of inertia of the sphere when axis
of rotation is located at its center is 0.08 kg-m2
, find the mass of the sphere.
A 9 kg solid cylinder has a radius 0.10m and thickness 5 cm. the axis of rotation is
located at the center of the cylinder. Compute for the moment of inertia.
What is the moment of inertial of a 3kg uniform rod with length 2 meters and radius
20cm, if the axis of rotation is located at (a) one end of the rod, (b) at the center of the
rod and (c) through the center?
