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2 years ago

1. All of the following show friction as a useful force, except _____.

2 answers:

7 0

1. Having to push a rough and heavy box across the floor to move it.
2. The coefficient of sliding friction will decrease.
3. Greater than the friction involved in rolling an object.
4. Drag.
5. Sliding (kinetic) friction. Sliding friction is also known as kinetic friction - force that is needed to keep a surface sliding along another surface.

ozzi2 years ago

4 0

1. having to push a rough and heavy box across the floor to move it

In this case, friction is not a useful force: in fact, our aim is to push the box across the floor and move it, while the direction of the friction is against the motion of the box, so this means that we have to do more work in order to win the friction and move the box.

2. The coefficient of sliding friction will stay the same.

In fact, the coefficient of sliding friction does not depend on the mass or the size of the object, but it depends only on the two materials which are in contact between each other (so, the material of the object and the material of the floor/surface).

3. the friction involved in sliding an object is greater than the friction involved in rolling an object

This can be explained by thinking that when sliding an object, the area of contact between the object and surface is generally larger than the area of contact when rolling an object (ideally, there is only one point of contact between the object and the surface when rolling an object), so friction has a greater effect.

4. drag

Drag is the frictional force exerted by a fluid (liquid or gas) on a solid object moving through the fluid. In particular, it is due to the contact between the surface of the object and the molecules of fluid: part of the energy of the object is transmitted to the molecules of the fluid, and the object decelerates.

5. kinetic friction

Kinetic friction is the force of reistance that occurs when an object is being pulled over a surface, and its formula is given by

$F_f = \mu m g$

where $\mu$ is the coefficient of friction, m is the mass of the object and g is the gravitational acceleration.

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While Bob is demonstrating the gravitational force on falling objects to his class, he drops an 1.0 lb bag of feathers from the

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As per the question Bob drops the bag full with feathers from the top of the building.

The mass of the bag(m)= 1.0 lb

Let the air resistance is neglected.As the bag is under free fall ,hence the only force that acts on the bag is the force of gravity which is in vertical downward direction.

Here the acceleration produced on bag due to the free fall will be nothing else except the acceleration due to gravity i.e g =9.8 m/s^2

Here we are asked to calculate the distance travelled by the bag at the instant 1.5 s

Hence time t= 1.5 s

From equation of kinematics we know that -

S=ut + 0.5at^2 [ here S is the distance travelled]

For motion under free fall initial velocity (u)=0.

Hence S= 0×1.5+{0.5×(-9.8)×(1.5)^2}

⇒ -S =0-11.025 m

⇒ S= 11.025 m

=11 m

Here the negative sign is taken only due to the vertical downward motion of the body .we may take is positive depending on our frame of reference .

Hence the correct option is B.

3 0

3 years ago

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What is the volume V of a sample of 4.00 mol of copper? The atomic mass of copper (Cu) is 63.5 g/mol, and the density of copper

rusak2 [61]

Answer : The volume of a sample of 4.00 mol of copper is $28.5cm^3$

Explanation :

First we have to calculate the mass of copper.

$\text{ Mass of copper}=\text{ Moles of copper}\times \text{ Molar mass of copper}$

$\text{ Mass of copper}=(4.00moles)\times (63.5g/mole)=254g$

Now we have to calculate the volume of copper.

Formula used :

$Density=\frac{Mass}{Volume}$

Now put all the given values in this formula, we get:

$8.92\times 10^3kg/m^3=\frac{254g}{Volume}$

$Volume=\frac{254g}{8.92\times 10^3kg/m^3}=2.85\times 10^{-2}L=2.85\times 10^{-2}\times 10^3cm^3=28.5cm^3$

Conversion used :

$1kg/m^3=1g/L\\\\1L=10^3cm^3$

Therefore, the volume of a sample of 4.00 mol of copper is $28.5cm^3$

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3 years ago

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What is the specific heat of the masses in this experiment? Infer the substance the masses are made of and explain your inferenc

horsena [70]

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3 years ago

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A spherical ball of charged particles has a uniform charge density. In terms of the ball's radius R, at what radial distances in

eimsori [14]

Answer:

Electric field at radius r inside the solid sphere is

Electric field at radius r between inner radius and outer radius of the shell is

E=0 N/C

Explanation:Given

The radius of the solid sphere is

The charge on the solid sphere is

The inner radius of the shell is

The outer radius of the shell is

The total charge on the shell is

PART(A)

The magnitude of electric field at radius r where \\The volumetric charge density of the solid sphere will be

The charge enclosed by the radius r inside the solid sphere is

rho=

According to gauss law

PART(B)

The electric field at radius r where

The shell is conducting so due to induction of charge

The charge induced on the inner surface of the shell is equal in magnitude of the total charge on the solid sphere but polarity will be changed because a conducting shell has no net electric field inside the shell

So,

The charge on the inner surface of the shell is

Due to conservation of the charge on the shell

The charge accumulated on the outer surface of the shell is

The charge enclosed by the radius r where

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2 years ago

Micah knows that a car had a change in velocity of 15 m/s.To determine acceleration ,Micah also needs the blank of the total tri

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Answer: To determine acceleration ,Micah also needs the Time of the total trip in seconds.

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$a = \frac{dv}{dt}$

for calculating acceleration, initial and final velocity are required in meter per second and the total time of the trip in seconds. Then acceleration is measured in meter per second square.

Thus, Micah knows that a car had a change in velocity of 15 m/s.To determine acceleration ,Micah also needs the Time of the total trip in seconds.

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3 years ago

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