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Magazine Problem 16
A sailboat, tied to a mooring with a line, weighs \(820 \mathrm{N}\) The mooring
line pulls horizontally toward the west on the sailboat with a force of $110
\mathrm{N}$. The sails are stowed away and the wind blows from the west. The
boat is moored on a still lake-no water currents push on it. Draw an FBD for
the sailboat and indicate the magnitude of each force.
Problem 17
A hummingbird is hovering motionless beside a flower. The blur of its wings shows that they are rapidly beating up and down. If the air pushes upward on the bird with a force of \(0.30 \mathrm{N},\) what is the weight of the hummingbird?
Problem 19
A model sailboat is slowly sailing west across a pond at $0.33 \mathrm{m} /
\mathrm{s} .\( A gust of wind blowing at \)28^{\circ}$ south of west gives the
sailboat a constant acceleration of magnitude $0.30 \mathrm{m} /
\mathrm{s}^{2}\( during a time interval of \)2.0 \mathrm{s} .$ (a) If the net
force on the sailboat during the 2.0 -s interval has magnitude $0.375
\mathrm{N},$ what is the sailboat's mass? (b) What is the new velocity of the
boat after the 2.0 -s gust of wind?
Problem 20
A man is lazily floating on an air mattress in a swimming pool. If the weight
of the man and air mattress together is \(806 \mathrm{N},\) what is the upward
force of the water acting on the mattress?
Problem 21
A bag of potatoes with weight \(39.2 \mathrm{N}\) is suspended from a string
that exerts a force of \(46.8 \mathrm{N}\). If the bag's acceleration is upward
at \(1.90 \mathrm{m} / \mathrm{s}^{2},\) what is the mass of the potatoes?
Problem 22
A 2010 -kg elevator moves with an upward acceleration of $1.50 \mathrm{m} /
\mathrm{s}^{2} .$ What is the force exerted by the cable on the elevator?
Problem 23
While an elevator of mass \(2530 \mathrm{kg}\) moves upward, the force exerted by the cable is \(33.6 \mathrm{kN} .\) (a) What is the acceleration of the elevator? (b) If at some point in the motion the velocity of the elevator is \(1.20 \mathrm{m} / \mathrm{s}\) upward, what is the elevator's velocity 4.00 s later?
Problem 24
The vertical component of the acceleration of a sailplane is zero when the air
pushes up against its wings with a force of \(3.0 \mathrm{kN}\). (a) Assuming
that the only forces on the sailplane are that due to gravity and that due to
the air pushing against its wings, what is the gravitational force on the
Earth due to the sailplane? (b) If the wing stalls and the upward force
decreases to \(2.0 \mathrm{kN}\) what is the acceleration of the sailplane?
Problem 25
A man lifts a 2.0 -kg stone vertically with his hand at a constant upward
velocity of \(1.5 \mathrm{m} / \mathrm{s} .\) What is the magnitude of the total
force of the man's hand on the stone?
Problem 26
A man lifts a 2.0 -kg stone vertically with his hand at a constant upward
acceleration of \(1.5 \mathrm{m} / \mathrm{s}^{2} .\) What is the magnitude of
the total force of the man's hand on the stone?
