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3 years ago

A student grabs a piece of paper and tears it from the middle. Which statement best explains the forces involved?

Physics

2 answers:

PolarNik [594]3 years ago

3 0

Answer:

b. The normal force between the molecules of the paper is overcome by the contact force of the hands.

Explanation:

The paper molecules are held together by a weak bond. When the student holds the paper on both sides with the center of the paper in between, the student applies two equal forces in the opposite direction of the paper making the paper molecules weaken and separate.

stich3 [128]3 years ago

3 0

Answer:

The electrostatic forces from the contact of the hands with the paper causes the paper molecules to separate.

Here's the rest of the answers

1.) Which statement is correct about the strength of forces?

Electrostatic forces are trillions of times stronger than gravitational forces.

2.) A student tries to push a book across a table. Which forces acting on the book are a result of electrostatic forces?

normal force and friction

3.) What type of force can explain how a gecko climbs up a wall?

contact forces

5.) A heavy hammer is sitting on top of a board. Which statement correctly describes why the hammer does not go through the board?

The electrostatic forces between the molecules of the board prevent the force of gravity from breaking the board apart.

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What provides the force on the person on the passenger seat?

Gennadij [26K]

There's the acceleration of the car that provides a force and the normal force of the seat cushion which pushes upwards against the passenger

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3 years ago

Describe the energy change in the particles of a substance during melting. A) The kinetic energy of the particles remains unchan

Rina8888 [55]

Answer:

As ice melts into water, kinetic energy is being added to the particles. This causes them to be 'excited' and they break the bonds that hold them together as a solid, resulting in a change of state: solid -> liquid.

Explanation:

As we may know, the change in state of an object is due to the change in the average kinetic energy of the particles.

This average kinetic energy is proportional to the temperature of the particles.

This is because heat is a form of energy; by adding energy to ice - heat, you "excite" the water molecules, breaking the interactions in the lattice structure and forming weaker, looser hydrogen-bonding interactions.

This causes the ice to melt. This is demonstrated in the image below.

More generally, when you remove energy - the object cools down, the particles move a lot slower. So slow, that they individually attract other molecules more than before, and this results in a physical change that also changes the state.

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3 years ago

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A 10 kg migratory swan cruises at 20m/s. A calculation that takes into ac-count the necessary forces shows that this motion requ

IgorC [24]

Answer:

Part A:

Distance=864000 m=864 km

Part B:

Energy Used=ΔE=8638000 Joules

Part C:

$\frac{\triangle m}{m}=0.004998=0.49985\%$

Explanation:

Given Data:

v=20m/s

Time =t=12 hours

In Secs:

Time=12*60*60=43200 secs

Solution:

Part A:

Distance = Speed**Time

Distance=v*t

Distance= 20*43200

Distance=864000 m=864 km

Part B:

Energy Used=ΔE= Energy Required-Kinetic Energy of swans

Energy Required to move= Power Required*time

Energy Required to move=200*43200=8640000 Joules

Kinetic Energy= $\frac{1}{2}mv^2$

$K.E\ of\ Swans=\frac{1}{2} *10*(20)^2=2000\ Joules$

Energy Used=ΔE=8640000 -2000

Energy Used=ΔE=8638000 Joules

Part C:

Fraction of Mass used=Δm/m

For This first calculate fraction of energy used:

Fraction of energy=ΔE/Energy required to move

ΔE is calculated in part B

Fraction of energy=8638000/8640000

Fraction of energy=0.99977

Kinetic Energy= $\frac{1}{2}mv^2$

Now, the relation between energies ratio and masses is:

$\frac{\triangle E}{E}=\frac{\triangle m}{2m}v^2$

$\frac{\triangle m}{m}=\frac{2}{v^2} *\frac{\triangle E}{E}\\\frac{\triangle m}{m}=\frac{2}{20^2} *0.99977$

$\frac{\triangle m}{m}=0.004998=0.49985\%$

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3 years ago

You are performing a knee extension exercise. You hold a 20kg weight at full knee extension. The weight is 0.4m from your knee j

dmitriy555 [2]

Answer:

The moment is -78.4 N-m (clockwise).

Explanation:

Given:

Mass of the object (m) = 20 kg

Distance of the object from the knee joint (d) = 0.4 m

Weight of leg is not considered.

Acceleration due to gravity (g) = 9.8 m/s²

Now, weight of the object is equal to the product of its mass and acceleration due to gravity. So,

Weight = Mass × Acceleration due to gravity

= $mg=20\times 9.8 =196\ N$

We know that, moment of a force about a point is defined as the product of force applied and the perpendicular distance between the point and the line of application of force.

Moment of the given weight about the knee joint is given as:

Moment about knee joint = Weight × Distance from knee joint to weight

Moment about knee joint = 196 × 0.4 = 78.4 Nm

Now, from the diagram below, we can observe that, the weight acts vertically down and thus the sense of rotation about the knee joint at point O is clockwise. So, moment is negative.

Therefore, the moment is -78.4 N-m (clockwise).

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3 years ago

Hey, I need help can someone help me out, please?

yan [13]

Explanation:

6) newton

7) f =ma = 15*15 = 225N

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3 years ago

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