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3 years ago

A boy of mass 60 kg runs up a staircase of 50 steps in 10s. If height of each steps is 12 cm,find the power

Physics

1 answer:

Alenkasestr [34]3 years ago

3 0

Answer:

350 W

Explanation:

50 steps × 0.12 m/step = 6 m

Power = work / time

P = mgh / t

P = (60 kg) (9.8 m/s²) (6 m) / 10 s

P = 352.8 W

Rounding to two significant figures, the power is 350 W.

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g A ball thrown straight up into the air is found to be moving at 7.94 m/s after falling 2.72 m below its release point. Find th

kati45 [8]

The ball has height y and velocity v at time t according to

y = v₀ t - 1/2 g t ²

and

v = v₀ - g t

where v₀ is its initial speed and g = 9.80 m/s² is the magnitude of the acceleration due to gravity.

The ball is falling with a velocity of 7.94 m/s when it's 2.72 m below the release point, which at time t such that

-2.72 m = v₀ t - 1/2 g t ²

-7.94 m/s = v₀ - g t

Solve for t in the second equation:

t = (v₀ + 7.94 m/s)/g

Substitute this into the first equation and solve for v₀ :

-2.72 m = v₀ (v₀ + 7.94 m/s) /g - 1/2 g ((v₀ + 7.94 m/s)/g)²

-2.72 m = v₀²/g + (7.94 m/s) v₀/g - 1/2 (v₀ + 7.94 m/s)²/g

2 (-2.72 m) g = 2v₀² + 2 (7.94 m/s) v₀ - (v₀ + 7.94 m/s)²

2 (-2.72 m) (9.80 m/s²) = 2v₀² + (15.9 m/s) v₀ - (v₀² + (15.9 m/s) v₀ + 63.0 m²/s²)

-53.3 m²/s² = v₀² - 63.0 m²/s²

v₀² = 9.73 m²/s²

v₀ = 3.12 m/s

3 0

2 years ago

Which statement is NOT true?

Nuetrik [128]

Answer:

light doesn't need a medium through which to travel because the speed of light is experimentally constant

4 0

2 years ago

What do we call the movement of electric charge? A. Power B. Voltage C. Resistance D. Current

Alex Ar [27]

D. Current

Hope I helped!

4 0

2 years ago

Read 2 more answers

An automobile engine delivers 47.4 hp. how much time will it take for the engine to do 6.82 × 105 j of work? one horsepower is e

kogti [31]

1 horsepower is equal to 746 W, so the power of the engine is
$P=47.4 hp \cdot 746 \frac{W}{hp}=35360 W$
The power is also defined as the energy E per unit of time t:
$P= \frac{E}{t}$
Where the energy corresponds to the work done by the engine, which is $E=6.82 \cdot 10^5 J$ . Re-arranging the formula, we can calculate the time t needed to do this amount of work:
$t = \frac{E}{P}= \frac{6.82 \cdot 10^5 J}{35360 W}=19.3 s$

8 0

3 years ago

Astronomers have observed a small, massive object at the center of our Milky Way Galaxy. A ring of material orbits this massive

Burka [1]

Answer:

$1.91773\times 10^{37}\ kg$

Explanation:

v = Orbital speed = 130 km/s

d = Diameter = 16 ly

r = Radius = $\dfrac{d}{2}=\dfrac{16}{2}=8\ ly$

G = Gravitational constant = 6.67 × 10⁻¹¹ m³/kgs²

$1\ ly=9.461\times 10^{15}\ m$

As the centripetal force balances the gravitational energy we have the following relation

$\dfrac{GMm}{r^2}=\dfrac{mv^2}{r}\\\Rightarrow M=\dfrac{v^2r}{G}\\\Rightarrow M=\dfrac{130000^2\times 8\times 9.461\times 10^{15}}{6.67\times 10^{-11}}\\\Rightarrow M=1.91773\times 10^{37}\ kg$

Mass of the the massive object at the center of the Milky Way galaxy is $1.91773\times 10^{37}\ kg$

4 0

3 years ago