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3241004551 [841]
4 years ago
9

A pencil is rolled off a table of height 1.25 m. If it has a horizontal speed of 3.1 m/s, how long does it take the pencil to re

ach the ground? A. 0.51 s B. 1.12 s C. 0.40 s D. 2.48 s
Physics
1 answer:
Darya [45]4 years ago
7 0
The horizontal speed has no effect on how long it takes to reach the ground.
A bullet shot from a gun and a bullet dropped from the front end of the gun
at the same time as the shot both hit the ground at the same time.

The number that counts is the height from which it fell . . . the 1.25 m.

I'll use this very useful formula:

       Distance of free fall,
       starting from rest            = (1/2) · (gravity) · (time)²

                                  1.25 m  =  (1/2) · (9.8 m/s²) · (time)²

Divide each side
by   4.9 m/s²  :          1.25 m / 4.9 m/s²  =  time²

                                          0.2551 sec²  =  time²

Square root each side:       0.505 sec  =  time

It looks like the correct choice is approximately 'A'. (rounded)
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3 years ago
A 15-µF capacitor and a 25-µF capacitor are connected in parallel, and charged to a potential difference of 60 V. How much energ
Alborosie

Answer:

Energy stored, E = 0.072 J

Explanation:

Given that,

Capacitance, C_1=15\ \mu F

Capacitance, C_2=25\ \mu F

These two capacitor are connected in parallel, and charged to a potential difference of, V = 60 volts

We know that in parallel combination of capacitor, the equivalent capacitance is given by :

C=C_1+C_2\\\\C=(15+25)\ \mu F\\\\C=40\times 10^{-6}\ F

The energy stored in the capacitor is given by :

E=\dfrac{1}{2}CV^2\\\\E=\dfrac{1}{2}\times 40\times 10^{-6}\times (60)^2\\\\E=0.072\ J

So, the energy stored in the capacitor in this capacitor combination is 0.072 J.

4 0
3 years ago
You are standing 30 m from a window that is 30 m off the ground. Your friend tries to toss you something, but only throws it str
pochemuha

Answer:

minimum initial velocity is 21.35 m/s

Explanation:

given data

distance S = 30 m

height h = 30 m

maximum acceleration a = 2 m/s²

to find out

minimum initial velocity that your friend could have thrown the object to enable you to catch

solution

first we get here time with the help of second equation of motion

time = \sqrt{\frac{2h}{a} }  ..................1

put her value we get

time = \sqrt{\frac{2*30}{2} }

time = 5.477 second

and that is time which tossed object must be take so we apply here again second equation of motion that is

-S = ut - 0.5 × gt²   .......................2

-30 = u× 5.477 - 0.5 ×9.8×5.477²

solve it we get

u = 21.35 m/s

so minimum initial velocity is 21.35 m/s

3 0
3 years ago
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