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gogolik [260]
3 years ago
13

Kelli weighs 440 N, and she is sitting on a playground swing that hangs 0.41 m above the ground. Her mom pulls the swing back an

d releases it when the seat is 1.00 m above the ground. Assume that air resistance is negligible. If Kelli moves through the lowest point at 2.0 m/s, how much work was done on the swing by friction
Physics
1 answer:
kifflom [539]3 years ago
4 0

Answer:

Explanation:

Initial height from the ground = .41 m

Final height = 1m

Height by which Kelli was raised ( h )= .59 m

When she passes through the lowest point , she loses P E

= mgh

= 440 x .59

= 259.6 J

kinetic energy possessed by her

= 1/2 mv²

= .5 x (440/9.8) x 2²

= 89.8 J

Difference of energy is lost due to work by  air friction

work done by  friction = 89.8 - 259.6

= - 169.8 J

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4 0
3 years ago
Which term describes a substance that has a low melting point and poor electrical conductivity?
densk [106]

Answer:Simple Covalent substance

Explanation:Simple covalent substance describes a substance that has a low melting point and poor electrical conductivity because:

(1)melting point :For the covalent bond and intermolecular force that are present in a simple covalent substance,energy is needed to break the forces of attraction present. In the simple covalent substance, little energy is needed because the intermolecular forces present are broken because they are weaker compared to the covalent bond present.

Therefore, when simple covalent substance melts,only the intermolecular forces are broken leaving only the covalent bond in the substance.

(2) poor conductivity: for a substance to conduct electricity,it must have charged particles which are free to move to and fro.

But in the simple covalent substance,there are no charged particles that can be separated due to the covalent bond present in simple covalent substance.

4 0
3 years ago
A helium balloon ride lifts up passengers in a basket. Assume the density of air is 1.28 kg/m3 and the density of helium in the
max2010maxim [7]

Answer:

V = 381.70 m³

Explanation:

ρ air = 1.28 kg / m³

ρ helium = 0.18 kg / m³

R = 4.5 m

Vb = 0.068 m³

mb = 123 kg

To determine the volume of helium in the balloon when fully inflated

V = 4 / 3 π * R ³

V = 4 * π / 3 ( 4.5 m )³

V = 381.70 m³

To determine the mass total

m = ρ helium * V

m = 0.18 kg / m³  * 381.70  m³

m = 68.70 kg

mt = ( 68.70 + 123 )kg

mt = 191.70 kg

3 0
3 years ago
Doc Brown holds on to the end of the minute hand of the clock atop city hall. The tangential velocity of the minute hand is 0.41
alexdok [17]

The Professor's centripetal acceleration is 0.044 m/s²

Centripetal acceleration is the acceleration of an object moving in circular motion. It is usually directed towards the center of the rotation.

It is given by:

a = v²/r

where v is the velocity and r is the radius.

Given that the radius (r) = 4 m, velocity (v) = 0.419 m/s, hence:

a = v²/r = 0.419²/4 =  0.044 m/s²

The Professor's centripetal acceleration is 0.044 m/s²

Find out more at: brainly.com/question/6082363

3 0
3 years ago
What is the mass of a stone moving at a speed of 15 meters/second and having a momentum of 7.5 kilogram - meters / seconds
Elanso [62]

Answer:

0.5 kg

Explanation:

The momentum of an object is defined as

p = mv

where

m is the mass

v is the velocity

In this problem we have,

v = 15 m/s is the velocity of the stone

p = 7.5 kg m/s is the momentum

Solving for m, we can find the mass of the stone:

m=\frac{p}{v}=\frac{7.5 kg m/s}{15 m/s}=0.5 kg

4 0
3 years ago
Read 2 more answers
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