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aliina [53]
4 years ago
13

On a stopwatch, the tip of the second hand moves 2 cm in 15 seconds. How long is the second hand (to the nearest tenth)? A. 1.3

cm. B. 6.3 cm. C. 12.6 cm. D. 30.0 cm
Physics
2 answers:
never [62]4 years ago
8 0
We are asked to determine the length of the second hand when it has moved 2 cm in 15 seconds. The movement in 15 seconds generates an angle of 90 degrees or pi / 2. we apply the equation of arc length which is 2 cm; s = 2= r theta = r* pi /2 where r is the second hand length. The answer is 1.27 cm closest to A
aalyn [17]4 years ago
4 0
Clever question.  Pretty simple, but we never think of the details
quite in this order.

-- The 'seconds' hand on the watch goes all the way around in 1 minute.
The tip of the hand moves in a circle.

-- 15 seconds is 1/4 of a complete 1-minute revolution. 
So the 2 cm is 1/4 of the way around the circle that the tip makes.

--  The full circumference of the circle is 8cm.

-- The length of the second hand is the radius of the circle. 

                              2 pi radius  =  circumference

                               2 pi radius  =  8 cm
Divide each side
by  2 pi :                        radius  =  8cm / 2 pi  =  1.27 cm
                                                                             (choice - A)
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slader How much energy is required to move a 1040 kg object from the Earth's surface to an altitude four times the Earth's radiu
andrew-mc [135]

Answer:

ΔU = 5.21 × 10^(10) J

Explanation:

We are given;

Mass of object; m = 1040 kg

To solve this, we will use the formula for potential energy which is;

U = -GMm/r

But we are told we want to move the object from the Earth's surface to an altitude four times the Earth's radius.

Thus;

ΔU = -GMm((1/r_f) - (1/r_i))

Where;

M is mass of earth = 5.98 × 10^(24) kg

r_f is final radius

r_i is initial radius

G is gravitational constant = 6.67 × 10^(-11) N.m²/kg²

Since, it's moving to altitude four times the Earth's radius, it means that;

r_i = R_e

r_f = R_e + 4R_e = 5R_e

Where R_e is radius of earth = 6371 × 10³ m

Thus;

ΔU = -6.67 × 10^(-11) × 5.98 × 10^(24)

× 1040((1/(5 × 6371 × 10³)) - (1/(6371 × 10³))

ΔU = 5.21 × 10^(10) J

7 0
3 years ago
A child looked at
fgiga [73]
The answer to your question is A.
4 0
2 years ago
Suppose that the average U.S. household uses 15600 kWh (kilowatt‑hours) of energy in a year. If the average rate of energy consu
sweet [91]

Answer:

a) 166.4 s

b) (2.155 × 10⁷) s

Explanation:

15600 KWh for a year,

1 year consists of 365 × 24 hours = 8760 hours.

So, the power consumed in a year for an average household = (Energy/time)

= (15600/8760) = 1.781 KW = 1781 W

a) If the average rate of energy consumed by the house was instead diverted to lift a 1.80 × 10 3 kg car 16.8 m into the air, how long would it take

The power required for this lifting = (mgh/t)

m = 1800 kg

g = 9.8 m/s²

h = 16.8 m

t = ?

P = 1781 W

1781 = (1800×9.8×16.8)/t

t = (296,352/1781)

t = 166.4 s

b) how long would it take to lift a loaded Boeing 747 airplane, with a mass of 4.05 × 10 5 kg , to a cruising altitude of 9.67 km

The power required for this lifting = (mgh/t)

m = 405000 kg

g = 9.8 m/s²

h = 9.67 km = 9670 m

t = ?

P = 1781 W

1781 = (405000×9.8×9670)/t

t = (38,380,230,000/1781)

t = 21,549,820 s = (2.155 × 10⁷) s

Hope this Helps!!!

8 0
3 years ago
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