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4 years ago

If you push a chair across the floor at a cibstant velocity how does the force of friction compare with the force you exert?

1 answer:

7 0

-- "constant velocity"   ===> acceleration is 0 .

-- acceleration=0   ===>   forces are balanced

-- balanced forces   ===> (friction) + (force you exert) = 0

   (friction) = -(force you exert)

They have equal magnitude and opposite direction.

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In some cases, neither of the two equations in the system will contain a variable with a coefficient of 1, so we must take a fur

Margaret [11]

Answer:

D = -4/7 = - 0.57

C = 17/7 = 2.43

Explanation:

We have the following two equations:

$3C + 4D = 5\ --------------- eqn (1)\\2C + 5D = 2\ --------------- eqn (2)$

First, we isolate C from equation (2):

$2C + 5D = 2\\2C = 2 - 5D\\C = \frac{2 - 5D}{2}\ -------------- eqn(3)$

using this value of C from equation (3) in equation (1):

$3(\frac{2-5D}{2}) + 4D = 5\\\\\frac{6-15D}{2} + 4D = 5\\\\\frac{6-15D+8D}{2} = 5\\\\6-7D = (5)(2)\\7D = 6-10\\\\D = -\frac{4}{7}$

D = - 0.57

Put this value in equation (3), we get:

$C = \frac{2-(5)(\frac{-4}{7} )}{2}\\\\C = \frac{\frac{14+20}{7}}{2}\\\\C = \frac{34}{(7)(2)}\\\\C = \frac{17}{7}\\$

C = 2.43

5 0

3 years ago

Starting from rest, a small block of mass m slides frictionlessly down a circular wedge of mass M and radius R which is placed o

guapka [62]

Answer:

Part a)

$V = \sqrt{\frac{2\frac{m}{M}gR}{(\frac{M}{m} + 1)}}$

$v = \frac{M}{m}\sqrt{\frac{2\frac{m}{M}gR}{(\frac{M}{m} + 1)}}$

Part b)

Since on the block wedge system there is no external force in horizontal direction so the Center of mass will not move in horizontal direction but in vertical direction it will move

so displacement in Y direction is given as

$y_{cm} = \frac{mR}{m + M}$

Explanation:

PART A)

As we know that there is no external force on the system of two masses in horizontal direction

So here the two masses will have its momentum conserved in horizontal direction

So we have

$mv + MV = 0$

Also we know that here no friction force on the system so total energy will always remains conserved

So we have

$\frac{1}{2}mv^2 + \frac{1}{2}MV^2 = mgR$

now we have

$\frac{1}{2}m(\frac{MV}{m})^2 + \frac{1}{2}MV^2 = mgR$

$\frac{1}{2}MV^2(\frac{M}{m} + 1) = mgR$

so we have

$V = \sqrt{\frac{2\frac{m}{M}gR}{(\frac{M}{m} + 1)}}$

and another block has speed

$v = \frac{M}{m}\sqrt{\frac{2\frac{m}{M}gR}{(\frac{M}{m} + 1)}}$

Part b)

Since on the block wedge system there is no external force in horizontal direction so the Center of mass will not move in horizontal direction but in vertical direction it will move

so displacement in Y direction is given as

$y_{cm} = \frac{mR}{m + M}$

7 0

3 years ago

A piston–cylinder assembly contains 5.0 kg of air, initially at 2.0 bar, 30 oC. The air undergoes a process to a state where th

vlada-n [284]

Answer:

Explanation:

The process is isothermic, as P V = constant .

work done = 2.303 n RT log P₁ / P₂

= 2.303 x 5 / 29 x 8.3 x 303 log 2 / 1 kJ

= 300.5k J

This energy in work done by the gas will come fro heat supplied as internal energy is constant due to constant temperature.

heat supplied = 300.5k J

specific volume is volume per unit mass

v / m

pv = n RT

pv = m / M RT

v / m = RT / p M

specific volume = RT / p M

option B is correct.

5 0

3 years ago

Which statement best describes Cleo's mistake? Light travels through air and water in angled, scattered paths. Light does not ch

pashok25 [27]

The question (obtained from the internet);

Cleo stated that light travels through air in straight paths, and when it moves from air to water, light changes direction, speeds up, and bends towards the normal

Answer:

The statement that best describes Cleo's mistake is;

Light slows down when it moves from air into water

Explanation:

The question;

Cleo stated that light travels through air in straight paths, and when it moves from air to water, light changes direction, speeds up, and bends towards the normal

The speed of light in water = 225,000 km/s

The speed of light in air = 299,702,547 m/s

The speed of light in vacuum = 299,792,458 m/s

Therefore, light slows down when it moves from a less dense medium to a denser medium

Light moves closer (bends) towards the normal when it moves from air into water. Light therefore, changes direction, and light moves in straight path which is known as rectilinear motion

Therefore, the statement that describes Cleo's mistake is that light actually slows down when it moves from air into water.

5 0

3 years ago

f a wave has a wavelength of 9 meters and a period of 0.006, what is the velocity of the wave? A. 1,200 m/s B. 1,500 m/s C. 1,80

GalinKa [24]

Answer: 1500 m/sec. ( b )

Solution:

V= f (λ)

Speed = frequency. Wavelength

And frequency = 1/time period

First we will find the frequency :

Frequency = 1/time period

1/0.006 = 166.67 Hz

Using this in the equation:

Speed = frequency. Wavelength

V= f (λ)

9 × 166.67

= 1500.03 ≈ 1500

V (Speed) = 1500 m/s.

Note: Do not forget to mention the units or otherwise they may cost you marks!

6 0

3 years ago

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