6. The
only two forces acting on a body have magnitudes of 20 N and 35 N and
directions that differ by 80°. The resulting acceleration has a
magnitude of 20 m/s2. What is the » mass of the body?
7. A student lifts a box
of fresh roses, which just arrived
from Mexico, 1.5 m in 3.0 second. If she lifts the
box the same distance in 6.0
second, the work done by her is:A. the same B. two times as great C. half as great D. one-fourth as great?
10. A 30-kg child rides on a circus Ferris wheel
that takes her around a vertical circular path with a radius of 20 m every 22
s. What is the magnitude of the
resultant force on the child at the highest point on this trajectory?
13. You
have a machine that can accelerate pucks on frictionless ice. In time t the puck travels a distance x when force F is applied. If force 3F is applied, in time t, the distance the box travels?
17. When a certain rubber band is stretched a distance x,
it exerts a restoring force of
magnitude F = Ax, where A is a constant whose value depends on
the stiffness of the rubber band. The work done by a student in stretching this
rubber band from x = 0 to x = L is:
23. A hole Is drilled to
the center of the Earth and a stone is dropped into it. When the stone is at
the Earth’s
center, compared with the value at the Earth’s surface? A. its mass and weight are both
changed B. its mass and weight are both zero C. its mass is unchanged and its weight is
zero D.
its mass is unchanged and its weight approaches infinity its mass is
unchanged and its weight
is indeterminable.