PHYS 101- HW 4 EXAM QUESTIONS AND ANSWERS ALREADY PASSED GRADED A+
A railroad diesel engine weighs four times as much as a freight car. If the diesel engine coasts
at 4.8 km/h into a freight car that is initially at rest, find the speed of the coupled cars. -
Answersbefore: p rail= 4(4.8) p car= w(0)
TOTAL P= 19.2 + 0 = 19.2
after: p= 5(?)
19.2 = 5x
x = 3.84 km/h
Two identical objects in outer space, one moving at 2 m/s, the other at 1 m/s, have a head-on
collision and stick together. Their combined speed after the collision is - Answersbefore: p 1=
5(2) p 2= -5(1)
TOTAL P= 10 - 5 = 5
after: p= 10v
v=0.5 m/s
Two 5000-kg rail cars roll without friction (one at 1 m/s, the other at 2 m/s) toward each other
on a level track. They collide, couple, and roll together with a combined momentum of -
Answersp 1= 5000(-1) p 2= 5000(2)
TOTAL P= -5000 + 10000 = 5000
Can a machine multiply input force? Input distance? Input energy? - Answersforce: yes, distance:
yes, energy: no
Relative to an initial height, an object raised twice as high has a gravitational potential energy...
twice as much
four times as much
half as much
need more information - Answerstwice as much
Emily holds a banana of mass m over the edge of a bridge of height h. She drops the banana
and it falls to the river below. Use conservation of energy to find the speed of the banana just
, before hitting the water. - Answersmgh = 1/2m(v^2)
divide by "m"
gh = 1/2(v^2)
multiply by 2
2gh = v^2
square root
v = SQRT(2gh)
Consider an ideal pulley system. If you pull one end of the rope 1.0 mm downward with a 44-N
force, find the height you can lift a 150-N load. - Answers44/150 = .29 x 1.0 = .29 m
The second floor of a house is 6 mm above the street level. How much work is required to lift a
310-kg refrigerator to the second-story level? - AnswersF=ma
w=mad
w = 310(10)(6) = 18600 J
On a rotating turntable, how do tangential speed and rotational speed vary with distance from
the center?
Both increase in speed with distance
Both are constant
Tangential speed increases with distance. Rotational speed is constant
Rotational speed increases with distance. Tangential speed is constant. - AnswersTangential
speed increases with distance. Rotational speed is constant
A tapered cup rolled on a flat surface makes a circular path. What does this tell you about the
tangential speed of the rim of the wide end of the cup compared with that of the rim of the
narrow end?
The tangential speed of the wide end is slower
The tangential speed of the wide end is zero
A railroad diesel engine weighs four times as much as a freight car. If the diesel engine coasts
at 4.8 km/h into a freight car that is initially at rest, find the speed of the coupled cars. -
Answersbefore: p rail= 4(4.8) p car= w(0)
TOTAL P= 19.2 + 0 = 19.2
after: p= 5(?)
19.2 = 5x
x = 3.84 km/h
Two identical objects in outer space, one moving at 2 m/s, the other at 1 m/s, have a head-on
collision and stick together. Their combined speed after the collision is - Answersbefore: p 1=
5(2) p 2= -5(1)
TOTAL P= 10 - 5 = 5
after: p= 10v
v=0.5 m/s
Two 5000-kg rail cars roll without friction (one at 1 m/s, the other at 2 m/s) toward each other
on a level track. They collide, couple, and roll together with a combined momentum of -
Answersp 1= 5000(-1) p 2= 5000(2)
TOTAL P= -5000 + 10000 = 5000
Can a machine multiply input force? Input distance? Input energy? - Answersforce: yes, distance:
yes, energy: no
Relative to an initial height, an object raised twice as high has a gravitational potential energy...
twice as much
four times as much
half as much
need more information - Answerstwice as much
Emily holds a banana of mass m over the edge of a bridge of height h. She drops the banana
and it falls to the river below. Use conservation of energy to find the speed of the banana just
, before hitting the water. - Answersmgh = 1/2m(v^2)
divide by "m"
gh = 1/2(v^2)
multiply by 2
2gh = v^2
square root
v = SQRT(2gh)
Consider an ideal pulley system. If you pull one end of the rope 1.0 mm downward with a 44-N
force, find the height you can lift a 150-N load. - Answers44/150 = .29 x 1.0 = .29 m
The second floor of a house is 6 mm above the street level. How much work is required to lift a
310-kg refrigerator to the second-story level? - AnswersF=ma
w=mad
w = 310(10)(6) = 18600 J
On a rotating turntable, how do tangential speed and rotational speed vary with distance from
the center?
Both increase in speed with distance
Both are constant
Tangential speed increases with distance. Rotational speed is constant
Rotational speed increases with distance. Tangential speed is constant. - AnswersTangential
speed increases with distance. Rotational speed is constant
A tapered cup rolled on a flat surface makes a circular path. What does this tell you about the
tangential speed of the rim of the wide end of the cup compared with that of the rim of the
narrow end?
The tangential speed of the wide end is slower
The tangential speed of the wide end is zero
