You can stop a mosquito travelling at a certain speed towards you by intercepting it with your
hand. Can you do the same for a car moving at the same speed as a mosquito? Discuss this
scenario using your knowledge on momentum and impulse. Give examples of
Discuss the features of dead-sea in terms of buoyancy, density, and general fluid mechanics
knowledge. If you were to reverse the properties of dead-sea, what could you do?
The Archimedes Principle says that when an object is completely or partially immer
A man walking on a tightrope carries a long a pole which has heavy items attached to the two
ends. If he were to walk the tight-rope with just a pole, what difference would it make to his
balance? Discuss this in terms of angular rotation, angular momentu
Physics, 6th Edition
Chapter 5 Torque and Rotational Equilibrium
5-12. Find the resultant torque in Fig. 5-13, if the axis is moved to the left end of the bar.
= +(30 N)(0) + (15 N)(4 m) - (20 N)(9 m)
15 N
A 4m
2m
3m
= -120 N m, counterclockwise.
30 N
4
Physics, 6th Edition
Chapter 5 Torque and Rotational Equilibrium
5-14. Two wheels of diameters 60 cm and 20 cm are fastened together and turn on the same axis
as in Fig. 5-14. What is the resultant torque about a central axis for the shown weights?
r1 = (
Physics, 6th Edition
Chapter 5 Torque and Rotational Equilibrium
5-15. Suppose you remove the 150-N weight from the small wheel in Fig. 5-14. What new
weight can you hang to produce zero resultant torque?
= (200 N)(0.30 m) W (0.15 m) = 0;
50
W = 400 N
Physics, 6th Edition
Chapter 6 Uniform Acceleration
*6-63. A wild boar charges directly toward a hunter with a constant speed of 60 ft/s. At the
instant the boar is 100 yd away, the hunter fires an arrow at 300 with the ground. What
must be the velocity o
Physics, 6th Edition
Chapter 5 Torque and Rotational Equilibrium
5-3. Determine the moment arm if the axis of rotation is at point A in Fig. 5-11b. What is the
F
magnitude of the moment arm?
rB = (2 m) sin 60
0
600
rB = 1.73 m
B
300
2m
A
38
5m
rA
rB
Physics, 6th Edition
Chapter 5 Torque and Rotational Equilibrium
5-1. Draw and label the moment arm of the force F about an axis at point A in Fig. 5-11a. What
is the magnitude of the moment arm?
rA
Moment arms are drawn perpendicular to action line:
A
rA
Physics, 6th Edition
Chapter 5 Torque and Rotational Equilibrium
5-6. The force F in Fig. 5-11b is 400 N and the angle iron is of negligible weight. What is the
resultant torque about axis A and about axis B?
Counterclockwise torques are positive, so that
Physics, 6th Edition
Chapter 5 Torque and Rotational Equilibrium
5-5. If the force F in Fig. 5-11a is equal to 80 lb, what is the resultant torque about axis A
neglecting the weight of the rod. What is the resultant torque about axis B?
Counterclockwise t
Physics, 6th Edition
Chapter 5 Torque and Rotational Equilibrium
5-13. What horizontal force must be exerted at point A in Fig 5-11b to make the resultant torque
about point B equal to zero when the force F = 80 N?
F = 80 N
= P (2 m) (80 N)(5 m) (sin 300
Physics, 6th Edition
Chapter 5 Torque and Rotational Equilibrium
5-8. The light rod in Fig. 5-12 is 60 cm long and pivoted about point A. Find the magnitude and
sign of the torque due to the 200 N force if is (a) 900, (b) 600, (c) 300, and (d) 00.
= (200
Physics, 6th Edition
Chapter 5 Torque and Rotational Equilibrium
5-9. A person who weighs 650 N rides a bicycle. The pedals move in a circle of radius 40 cm. If
the entire weight acts on each downward moving pedal, what is the maximum torque?
= (250 N)(0
Physics, 6th Edition
Chapter 5 Torque and Rotational Equilibrium
5-10. A single belt is wrapped around two pulleys. The drive pulley has a diameter of 10 cm,
and the output pulley has a diameter of 20 cm. If the top belt tension is essentially 50 N at
the
Physics, 6th Edition
Chapter 5 Torque and Rotational Equilibrium
5-11. What is the resultant torque about point A in Fig. 5-13. Neglect weight of bar.
= +(30 N)(6 m) - (15 N)(2 m) - (20 N)(3 m)
15 N
4m
= 90.0 N m, Counterclockwise.
30 N
46
3m
2m
A
20 N
Physics, 6th Edition
Chapter 5 Torque and Rotational Equilibrium
5-7. A leather belt is wrapped around a pulley 20 cm in diameter. A force of 60 N is applied to
the belt. What is the torque at the center of the shaft?
r = D = 10 cm;
= (60 N)(0.10 m) = +6
Physics, 6th Edition
Chapter 6 Uniform Acceleration
6-46. A ball is thrown vertically upward with an initial velocity of 23 m/s. What are its
position and velocity after 2s, after 4 s, and after 8 s?
Apply s = vot + at2 and vf = vo + at
for time of 2, 4,
Physics, 6th Edition
Chapter 6 Uniform Acceleration
*6-59. A ball is dropped from rest at the top of a 100-m tall building. At the same instant a
second ball is thrown upward from the base of the building with an initial velocity of 50
m/s. When will the
Physics, 6th Edition
Chapter 6 Uniform Acceleration
6-48. A ball is thrown vertically upward with an initial velocity of 80 ft/s. What are its
position and velocity after (a) 1 s; (b) 3 s; and (c) 6 s
Apply s = vot + at2 and vf = vo + at
for time of 2, 4,
Physics, 6th Edition
Chapter 6 Uniform Acceleration
*6-50. In Problem 6-49, what was the horizontal range of the package and what are the
components of its final velocity?
vo = 500 mi/h = 733 ft/s;
vx = vox = 733 ft/s;
x = vxt = (733 ft/s)(4 s);
vy = voy
Physics, 6th Edition
Chapter 6 Uniform Acceleration
6-47. A stone is thrown vertically downward from the top of a bridge. Four seconds later it
strikes the water below. If the final velocity was 60 m/s. What was the initial velocity of
the stone and how h
Physics, 6th Edition
Chapter 6 Uniform Acceleration
6-52. A long strip of pavement is marked off in 100-m intervals. Students use stopwatches to
record the times a car passes each mark. The following data is listed:
Distance, m
Time, s
0
10 m
20 m
30 m
40
Physics, 6th Edition
Chapter 6 Uniform Acceleration
*6-51. A putting green is located 240 ft horizontally and 64 ft vertically from the tee. What
must be the magnitude and direction of the initial velocity if a ball is to strike the green
at this location
Physics, 6th Edition
Chapter 6 Uniform Acceleration
6-53. An astronaut tests gravity on the moon by dropping a tool from a height of 5 m. The
following data are recorded electronically.
Height, m
Time, s
5.00 m
4.00 m
3.00 m
2.00 m
1.00 m
0m
0
1.11 s
1.56
Physics, 6th Edition
Chapter 6 Uniform Acceleration
*6-56. The acceleration due to gravity on an distant planet is determined to be one-fourth its
value on the earth. Does this mean that a ball dropped from a height of 4 m above this
planet will strike th
Physics, 6th Edition
Chapter 6 Uniform Acceleration
*6-54. A car is traveling initially North at 20 m/s. After traveling a distance of 6 m, the car
passes point A where it's velocity is still northward but is reduced to 5 m/s.
(a) What
are the magnitude a
Physics, 6th Edition
Chapter 6 Uniform Acceleration
*6-55. A ball moving up an incline is initially located 6 m from the bottom of an incline and has
a velocity of 4 m/s. Five seconds later, it is located 3 m from the bottom. Assuming
constant acceleratio
Physics, 6th Edition
Chapter 6 Uniform Acceleration
*6-57. Consider the two balls A and B shown in Fig. 6-15. Ball A has a constant acceleration of
4 m/s2 directed to the right, and ball B has a constant acceleration of 2 m/s2 directed to
the left. Ball A
Discuss the differences in North Pole and the magnetic North Pole, and the South Pole and the
magnetic South Pole in terms of dip angle and magnetic declination. Discuss the cause of
northern lights.
The Earth acts as a magnet which causes the magnetic fi
Visit the following website:
http:/www.wired.com/gadgetlab/2008/08/vertical-windsp/
Discuss the claims in terms of Carnot engine and other thermodynamic principles.
In a thermodynamic process heat flows from a hotter object to a cooler object. A heat engi
Describe in detail the difference between electric potential and potential energy by giving
examples and presenting relevant formulae.
Electric potential energy is the work done on a charged particle that is moving in an electric
field. This depends on th
What is a superconductor? Discuss this in terms of resistance and current.
A superconductor is an object that can conduct electricity or conduct electrons from one atom to
another with no resistance. There is no heat, sound or any other material that can
It is said, The lightning doesnt strike twice. Discuss this statement by first describing how the
lightning occurs in terms of electrostatic forces and approve or disapprove the above statement.
Lightning is a large spark of electricity in the atmosphere