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zloy xaker [14]

2 years ago

5

A ball is thrown upwards. Neglecting air resistance, what initial upward speed does the ball need to remain in the air for a tot

al time of 10 seconds

1 answer:

melamori03 [73]2 years ago

5 0

Answer:

H = 1/2 g t^2 time to reach top of trajectory

v = g t time to reach top of trajectory when v is initial speed upwards

v = 5 g = 49 m/s 5 sec upwards and 5 sec downwards

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konstantin123 [22]

Answer:

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3 years ago

A student at a window on the second floor of a dorm sees her physics professor walking on the sidewalk beside the building. she

klasskru [66]

Refer to the diagram shown below.

In order for the balloon to strike the professor's head, th balloon should drop by 18 - 1.7 = 16.3 m in the time at the professor takes to walk 1 m.
The time for the professor to walk 1 m is
t = (1 m)/(0.45 m/s) = 2.2222 s

The initial vertical velocity of the balloon is zero.
The vertical drop of the balloon in 2.2222 s is
h = (1/2)*(9.8 m/s²)*(2.2222 s)² = 24.197 m

Because 24.97 > 16.3, the balloon lands in front of the professor, and does not hit the professor.

The time for the balloon to hit the ground is
(1/2)*(9.8)*t² = 18
t = 1.9166 s

The time difference is 2.2222 - 1.9166 = 0.3056 s
Within this time interval, the professor travels 0.45*0.3056 = 0.175 m
Therefore the balloon falls 0.175 m in front of the professor.

Answer:
The balloon misses the professor, and falls 0.175 m in front of the professor.

8 0

3 years ago

Donde se hizo el “siluetazo”, <br>Me aydan

brilliants [131]

Answer:

La palabra silueta se deriva del nombre de Étienne de Silhouette, una ministra de finanzas francesa que, en 1759, se vio obligada por la crisis crediticia de Francia durante la Guerra de los Siete Años a imponer severas demandas económicas al pueblo francés, particularmente a los ricos.

Explanation:

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3 years ago

Which is likely to be more common in our Galaxy: white dwarfs or black holes? Why?

Nookie1986 [14]

Answer:

White dwarfs are likely to be much more common. The number of stars decreases with increasing mass, and only the most massive stars are likely to complete their lives as black holes. There are many more stars of the masses appropriate for evolution to a white dwarf.

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3 years ago

Which, if any, of the following statements about electric field lines is/are true? A.The electric field is always perpendicular

jonny [76]

The electric field is always perpendicular to the surface outside of a conductor. TRUE

<span> If an electron were placed on an electric field line, it would move in a direction perpendicular to the field. FALSE, it would move in an anti-parallel direction because its charge is negative </span>

<span>Electric field lines originate on positive charge and terminate on negative charge. TRUE ; but they can also go to infinity </span>

It is possible for two electric field lines to cross each other.
<span> Usually FALSE; though technically possible at special points where field is zero. </span>

If an electron and a positron were in the presence of a very strong electric field, they would move away from each other.
<span> TRUE; one is positive, and one is negative. If the field is strong enough, the action of the field will overcome the mutual attraction between them </span>

It is not possible for the electric field to ever be zero. FALSE: it IS possible, inside a conductor for instance

If a proton were placed on an electric field line, it would move in a direction anti-parallel to the field.
<span> FALSE: being positive, it would move in the SAME direction as the field</span>ic

8 0

3 years ago