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nadezda [96]
3 years ago
7

PLEASE HELP An object is thrown upward with an initial velocity of 32.1 m/s. What is its velocity in 4.0 s? (use g = 9.81 m/s2).

Please include step by step process. -7.14 11.2 7.14 -4.6
Physics
1 answer:
grigory [225]3 years ago
6 0

Answer:

-7.14

Explanation:

According to equation of motion

v = u + at

where

v is the final velocity at any time t

u is the initial velocity

a is the acceleration

and t is the time

___________________________________________

Given

An object is thrown upward it means

its initial velocity is in upward direction

but acceleration due to gravity is in downward direction which will cause to decrease the velocity of object.

Intial velocity u = 31.1 m/s

final velocity v at 4 second we have to find.

t = 4 second

a = g = 9.81 m/s2 (it is acting in opposite direction of motion hence its sign will be negative ).

Thus

a = -  9.81 m/s2

using the above values in v = u + at

v = 32.1 - 9.81*4

v = 32.1 - 39.24

v = -7.14

Thus, correct option is -7.14.

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biopsychlogy

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6 0
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If a 0.15 kg ball falls and has a KE of 20 J just before striking the ground, from what height did it fall. A. 1.36m B. 3m C. 13
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According to the conservation of mechanical energy, the kinetic energy just before the ball strikes the ground is equal to the potential energy just before it fell. 

Therefore, we can say KE = PE
We know that PE = m·g·h

Which means KE = m·g·h

We can solve for h:

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The correct answer is: the ball has fallen from a height of 13.6m.

5 0
3 years ago
. Each valve A, B, and C, when open, releases water into a tank at its own constant rate. With all three valves open, the tank f
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Answer:

Time taken by A and B is 1.2 hr.

Explanation:

Given that

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Time taken by tank when B+C are open = 2 hr

If we treat as filling of tank is a work then

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Lets take work is 1 unit

1 = 1(1/a+1/b+1/c)          ---------1

1 = 1.5(1/a+1/c)           ----------2

1 = 2(1/b+1/c)             --------3

From equation 1 and 3

1=1(1/a+1/2)

a=2

Form equation 2

1 = 1.5(1/2+1/c)

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From equation 3

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So time taken by

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B is alone to fill tank is 3 hr

C is alone to fill tank is 6 hr

So time\ taken\ by\ A\ and\ B =\dfrac{2\times 3}{2+3} hr

Time taken by A and B is 1.2 hr.

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masha68 [24]

Answer:

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