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3 years ago

I really need help with this

Physics

1 answer:

katen-ka-za [31]3 years ago

8 0

<u>C</u> is the correct answer, because energy cannot be created neither destroy. The energy is changing from chemical to from electric to light, and from light to heat.

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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

RUDIKE [14]

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:

h = KE / m·g
= 20 / (0.15 · 9.8)
= 13.6m

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

5 0

3 years ago

How many items are present in the compound (NH4)2Cr2O7

SVEN [57.7K]

In 2Cr2O7 there’s 2 items; Cr and O

5 0

3 years ago

A 57 kg pole vaulter running at 11 m/s vaults over the bar. Her speed when she is above the bar is 1.1 m/s. The acceleration of

kari74 [83]

Answer:

Her altitude as she crosses the bar, h₂ is approximately 6.1 m

Explanation:

The given parameters of the motion of the pole vaulter are;

The mass of the pole vaulter, m = 57 kg

The speed with which the pole vaulter is running, u = 11 m/s

The speed of the pole vaulter when she crosses the bar, v = 1.1 m/s

The acceleration due to gravity, g = 9.8 m/s²

From the total mechanical energy, M.E. equation, we have;

M.E. = P.E. + K.E.

Where;

P.E. = The potential energy of the motion = m·g·h

K.E. = The kinetic energy of the motion = 1/2·m·v²

By the principle of conservation of energy, we have;

The change (loss) in kinetic energy, ΔK.E. = The change (gain) in potential energy, ΔP.E.

ΔK.E. = 1/2·m·(v² - u²)

ΔP.E. = m·g·(h₂ - h₁)

Where;

h₁ = The ground level = 0 m

h₂ = The altitude with which she crosses the bar

∴ 1/2·m·(v² - u²) = m·g·(h₂ - h₁)

(h₂ - h₁) = (v² - u²)/(2·g) = (11² - 1.1²)/(2·9.8) = 6.11173469388

h₂ = 6.11173469388 + h₁ = 6.11173469388 + 0 = 6.11173469388

h₂ = 6.11173469388

Her altitude as she crosses over the bar, h₂ ≈ 6.1 m.

3 0

3 years ago

Car a with mass 1,783 kg collides with stationary 1600 kg car b. they become locked together after the collision and move with s

ValentinkaMS [17]

The initial speed of car A is 15.18 m/s.

Momentum is defined as mass in motion. If there are two objects (the two objects in motion or only one object in motion and the other in stationary) that collide and no other forces work in the system, the law of momentum conservation applies in the system.

p=p'

pa+pb = pa'+pb'

(ma×va) + (mb×vb) = (ma×va') + (mb×vb')

ma = mass of object A (kg) = 1,783 kg
mb = mass of object B (kg) = 1,600 kg
va = speed of object A before collides (m/s)
va' = speed of object A after collides (m/s) = 8 m/s
vb = speed of object B before collides (m/s) = 0 m/s
vb' = speed of object B after collides (m/s) = 8 m/s
p = momentum before collision (Ns)
p' = momentum after collision (Ns)

(ma×va) + (mb×vb) = (ma×va') + (mb×vb')

(1,783×va) + (1,600×0) = (1,783×8) + (1,600×8)

(1,783×va) + 0 = 14,264+12,800

(1,783×va) = 27,064

$va \:=\: \frac{27,064}{1.783}$

va = 15.18 m/s

Learn more about The law of momentum conservation here: brainly.com/question/7538238

#SPJ4

3 0

1 year ago

Why is the answer C?

4vir4ik [10]

Explanation:

We want to find the statement that is proven by the fact that the balls reach the same height.

A isn't supported by the evidence. Balls can reach the same height without having the same initial speed.

B isn't supported by the evidence. Balls can reach the same height without having the same launch angle.

C is supported. Projectiles spend the same amount of time going up as they do coming down, so if two projectiles reach the same height, then they must spend the same amount of time in the air.

D isn't supported by the evidence. Balls thrown at the same speed and complementary angles have the same range but different heights.

E isn't supported by the evidence. The mass of the ball doesn't affect the height.

7 0

3 years ago