Assignment for Crackcode only
Otrava501
Ivy Bucsa
102- PHY
August 3, 2014
Lillian Flakes
Chapter One and Two Assignments
Think and Solve
40) Find the net force produced by a 30-N force and a 20-N force in each of these cases:
(a) Both forces act in the same direction.
(b) The two forces act in opposite directions.
45) A horizontal force of 120N is required to push a bookcase across a floor of constant velocity
(a) What is the net force acting on the bookcase?
(b) How much is the friction force that acts on the sliding bookcase?
(c) How much friction acts on the bookcase when it is at rest on a horizontal surface without being pushed?
48) (a) Show the average speed of a tennis ball is 48 m/s when it travel the full length of the court, 24m in 0.5 s.
49) (a) Show the average speed that the average speed of Leslie is 10 km/h when she runs to the store 5km away in 30min
50) (a) Show that the acceleration is 7.5 m/s for a ball that starts from rest and rolls down a ramp and gains a speed of 30 m/s in 4s.
Exercise 91
For a freely falling object dropped from rest, what is acceleration at the end of 5s.
Discussion Questions
100) Henry the painter swings year after year from his bosun’s chair. His weight is 500N and the rope unknown to him has a breaking point of 300N. Why doesn’t the rope break when he is supported shown on the left? One day Harry was painting near a flagpole for a change, he tied the free end of the rope to the flagpole instead of his chair as shown right. Discuss with your friend why Harry took his vacation early.
106) Two balls A and B are released simultaneously from rest at left end of equal-length tracks, as shown. Which ball, A or B, will reach the end of the track first?
107) Refer to the preceding question.
(a) Does ball B roll faster along the lower part of its track than ball A along its straighter track?
(b) Is the speed gained by ball B going down the extra dip the same as the speed it loses going up near the right hand end --- and doesn’t this mean that the speeds of balls A and B will be the same at both ends of the tracks?
(c) For ball B won’t the average speed dipping down and up be greater than the average speed of ball A during the same time?
(d) So overall does ball A or B have the greater average speed? ( Do wish to change you answer to the preceding question?)
Chapter 2
Think and Solve
40) 40. An astronaut of mass 120 kg recedes from her spacecraft
by activating a small propulsion unit attached to her
back. The force generated by a spurt is 30 N. Show that
her acceleration is 0.25 m/s2.
42. Sophia exerts a steady 40-N horizontal force on a 8-kg
box resting on a lab bench. The box slides against a horizontal
friction force of 24 N. Show that the box accelerates
at 2 m/s2
44. A rocket of mass 100,000 kg undergoes an acceleration
of 2 m/s2. Show that the net force acting on it is
200,000 N
Exercise 69
69. If it were not for air resistance, would it be dangerous to
go outdoors on rainy days? Defend your answer
Disscusion Question
98. On which of these hills does the ball roll down with
increasing speed and decreasing acceleration along the
path? (Use this example if you wish to explain to someone
the difference between speed and acceleration.)
99. If you drop an object, its acceleration toward the ground
is 10 m/s2. If you throw it down instead, will its acceleration
after leaving your hand be greater than 10 m/s2?
Ignore air resistance. Defend your answer.
100. Can you think of a reason why the acceleration of the
object thrown downward through the air in the preceding
question would actually be less than 10 m/s2?
References
Arnold, J. B., & Dodge, H. W. (1994). Room for all. The American School Board Journal, 181(10), 22-26.
Black, J. A., & English, F. W. (1986). What they don’t tell you in schools of education about school administration. Lancaster, PA: Technomic.
Daresh, J. C. (2004). Beginning the assistant principalship: A practical guide for new school administrators. Thousand Oaks, CA: Corwin.
King, M., & Blumer, I. (2000). A good start. Phi Delta Kappan, 81(5), 356-360.
Seventeen moments in Soviet history. (n.d.). Retrieved from http://soviethistory.org/index.php? action=L2&SubjectID=1929collectivization&Year=1929