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Liono4ka [1.6K]
2 years ago
10

A ball is dropped from the top of a cliff. By the time it reaches the ground, all the energy in its gravitational potential ener

gy store has been transferred into its kinetic energy store. If the ball is travelling at 20 m/s when it hits the ground, what height was it dropped from? (Assume that the gravitational field strength is 10 N/kg.)
The answer is 20 meters, how do I get that?
Physics
1 answer:
gogolik [260]2 years ago
4 0

U = mgh, Ek = 1/2*m*v^2

U = Ek (conservation of mechanical energy)

⇒ mgh = 1/2*m*v^2

∵g = 10, v = 20

⇒ 10h = 1/2*400

⇒ h = 20 (m)

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Which is a process that involves collecting information and ideas that are supported by belief or opinion?
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3 years ago
A 190 g air-track glider is attached to a spring. The glider is pushed in 9.20 cm and released. A student with a stopwatch finds
Sholpan [36]

Answer:

k = 12.136\,\frac{N}{m}

Explanation:

The angular frequency of the system is:

\omega = \sqrt{\frac{k}{m} }

The frequency is:

f = \frac{14\,osc}{11\,s}

f = 1.272\,hz

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\omega = 2\pi\cdot (1.272\,hz)

\omega = 7.992\,\frac{rad}{s}

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k = \left(7.992\,\frac{rad}{s} \right)^{2}\cdot (0.190\,kg)

k = 12.136\,\frac{N}{m}

6 0
3 years ago
1. Two charges Q1( + 2.00 μC) and Q2( + 2.00 μC) are placed along the x-axis at x = 3.00 cm and x=-3 cm. Consider a charge Q3 of
Masja [62]

Answer:

speed when it reaches y = 4.00cm is

v = 14.9 g.m/s

Explanation:

given

q₁=q₂ =2.00 ×10⁻⁶

distance along x = 3.00cm= 3×10⁻²

q₃= 4×10⁻⁶C

mass= 10×10 ⁻³g

distance along y = 4×10⁻²m

r₁ = \sqrt{3^{2} +2^{2}  } = \sqrt{13} = 3.61cm = 0.036m

r₂ = \sqrt{4^{2} + 3^{2}  } = \sqrt{25} = 5cm = 0.05m

electric potential V = \frac{kq}{r}

change in potential ΔV = V_{1} - V_{2}

ΔV = \frac{2kq_{1} }{r_{1}} - \frac{2kq_{2} }{r_{2} } , where q_{1} = q_{2}=2.00μC

ΔV = 2kq(\frac{1}{r_{1}} - \frac{1}{r_{2} })

ΔV = 2 × 9×10⁹ × 2×10⁻⁶ × (\frac{1}{0.036} - \frac{1}{0.05} )

ΔV= 2.789×10⁵

\frac{1}{2}mv^{2} = ΔV × q₃

\frac{1}{2} ˣ 10×10⁻³ ×v² = 2.789×10⁵× 4 ×10⁻⁶

v² = 223.12 g.m/s

v = 14.9 g.m/s

3 0
3 years ago
Use the information below to answer questions
Ulleksa [173]

Answer:

The charges are q₁  = 2 × 10⁻⁸ C and  q₂ = 3 × 10⁻⁸ C

Explanation:

Here is the complete question

Two identical tiny balls have charge q1 and q2. The repulsive force one exerts on the other when they are 20cm apart is 1.35 X 10-4 N. after the balls are touched together and then represented once again to 20cm, now the repulsive force is found to be 1.40 X 10-4 N. find the charges q1 and q2.

Solution

The force F = 1.35 × 10⁻⁴ N when the charges are separated a distance of r = 20 cm = 0.2 m is given by

F = kq₁q₂/r₁²

q₁q₂ = Fr₁²/k

q₁q₂ = 1.35 × 10⁻⁴ N × (0.2 m)²/9 × 10⁹ Nm²/C² = 0.054/9 × 10⁻¹³ C² = 0.006 × 10⁻¹³ C² = 6 × 10⁻¹⁶ C²

q₁q₂ = 6 × 10⁻¹⁶ C² (1)

When the charges are brought together, the charge is now q = (q₁ + q₂)/2

The new repulsive force F = 1.406 × 10⁻⁴ N  at a distance of r₂ = 20 cm = 0.2 m is then

F₂ = kq²/r₂²

q² = F₂r₂²/k = 1.406 × 10⁻⁴ N × (0.2 m)²/9 × 10⁹ Nm²/C² = 0.00625 × 10⁻¹³ C² = 6.25 × 10⁻¹⁶ C²

q² = 6.25 × 10⁻¹⁶ C²

q = √(6.25 × 10⁻¹⁶) C

q = 2.5 × 10⁻⁸ C

(q₁ + q₂)/2 =  2.5 × 10⁻⁸ C

(q₁ + q₂) = 2 × 2.5 × 10⁻⁸ C

q₁ + q₂ = 5 × 10⁻⁸ C (2)

q₁  = 5 × 10⁻⁸ C - q₂  (3)

Substituting equation (3) into (1), we have

(5 × 10⁻⁸ C - q₂)q₂ = 6 × 10⁻¹⁶ C²

Expanding the bracket, we have

(5 × 10⁻⁸ C)q₂ - q₂² = 6 × 10⁻¹⁶ C²

So, q₂² - (5 × 10⁻⁸ C)q₂ + 6 × 10⁻¹⁶ C² = 0

Using the quadratic formula to find q₂

q_{2} = \frac{-(-5 X 10^{-8} )+/- \sqrt{(-5 X 10^{-8} )^{2} - 4X1X6 X 10^{-16} } }{2X1}\\  = \frac{5 X 10^{-8} )+/- \sqrt{25 X 10^{-16}  - 24 X 10^{-16} } }{2}\\= \frac{5 X 10^{-8} )+/- \sqrt{1 X 10^{-16} } }{2}\\= \frac{5 X 10^{-8} )+/- 1 X 10^{-8} }{2}\\= \frac{5 X 10^{-8} + 1 X 10^{-8} }{2} or \frac{5 X 10^{-8}  - 1 X 10^{-8} }{2}\\= \frac{6 X 10^{-8} }{2} or \frac{4 X 10^{-8}}{2}\\= 3 X 10^{-8} C or 2 X 10^{-8} C

q₁  = 5 × 10⁻⁸ C - q₂

q₁  = 5 × 10⁻⁸ C - 3 × 10⁻⁸ C or 5 × 10⁻⁸ C - 2 × 10⁻⁸ C

q₁  = 2 × 10⁻⁸ C or 3 × 10⁻⁸ C

So the charges are q₁  = 2 × 10⁻⁸ C and  q₂ = 3 × 10⁻⁸ C

5 0
4 years ago
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