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geniusboy [140]

2 years ago

9

Experiments using "optical tweezers" measure the elasticity of individual DNA molecules. For small enough changes in length, the

elasticity has the same form as that of a spring. A DNA molecule is anchored at one end, then a force of 1.5nN (1.5×10−9N) pulls on the other end, causing the molecule to stretch by 5.0nm (5.0×10−9m). What is the spring constant of that DNA molecule?

1 answer:

GalinKa [24]2 years ago

8 0

Answer:

Spring constant, k = 0.3 N/m

Explanation:

It is given that,

Force acting on DNA molecule, $F=1.5\ nN=1.5\times 10^{-9}\ N$

The molecule got stretched by 5 nm, $x=5\times 10^{-9}\ m$

Let k is the spring constant of that DNA molecule. It can be calculated using the Hooke's law. It says that the force acting on the spring is directly proportional to the distance as :

$F=-kx$

$k=\dfrac{F}{x}$

$k=\dfrac{1.5\times 10^{-9}\ N}{5\times 10^{-9}\ m}$

k = 0.3 N/m

So, the spring constant of the DNA molecule is 0.3 N/m. Hence, this is the required solution.

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Mr. Chang's class participated in a science experiment where they placed three substances outside in the sunlight to determine w

Montano1993 [528]

Answer:

B or D but im pretty sure it is D

Explanation:

When molecules are left in the sun, it heats up. When molecules heat up, the begin to vibrate rapidly. The sun is not constant as it could get blocked by clouds, so it would, at times, slow down the movement of the molecules. The answer is most likely D.

7 0

2 years ago

Which statement is true?

iogann1982 [59]

B
Think of inertia of getting into a car accident without a seat belt although the car stops you will not you would likely fly out the window

7 0

1 year ago

Read 2 more answers

A 74.9 kg person sits at rest on an icy pond holding a 2.44 kg physics book. he throws the physics book west at 8.25 m/s. what i

never [62]

Answer:

The recoil velocity is 0.2687 m/s.

Explanation:

∵ The person is sitting on an icy surface , we can assume that the surface is frictionless.

∴ There is no force acting acting on the person and book as a system in horizontal direction.

Hence , momentum is conserved for this system in horizontal direction of motion.

If 'i' and 'f' be the initial and final states of this system , then by principle of conservation of momentum(p) -

$p_{i}$ = $p_{f}$

System initially is at rest

∴ $p_{i}$ =0

∴ From the above 2 equations

$p_{f}$ =0

We know that ,

Momentum(p)=Mass of the body(m)×velocity of the body(v)

Let $m_{1}$ and $m_{2}$ be the mass of the person and the book respectively and $v_{1}$ and $v_{2}$ be the final velocities of the person and book respectively.

∴ $p_{f}$ = $m_{1}$ $v_{1}$ + $m_{2}$ $v_{2}$ =0

From the question ,

$m_{1}$ = 74.9 kg

$m_{2}$ = 2.44 kg

$v_{2}$ = 8.25 m/s

Substituting these values in the above equation we get ,

(74.9 × $v_{1}$ )+ (2.44×8.25) = 0

∴ $v_{1}$ = - 0.2687 m/s (Negative sign suggests that the motion of the person is opposite to that of the book)

∴ The recoil velocity is 0.2687 m/s.

4 0

2 years ago

Kimonoski takes a 9-minute shower every day. The shower uses about 1.8 gal per minute of water. He also uses 23 gallons of hot w

ioda

Answer:

$Q_{week} = 458884.6\, BTU$

Explanation:

The weekly water consumption of Kimonoski is:

$m_{bath,week} = (62.4\,\frac{lbm}{ft^{3}})\cdot (1.8\,\frac{gal}{min} )\cdot (\frac{0.134\,ft^{3}}{1\,gal} )\cdot (\frac{1\,min}{60\,s} )\cdot (9\,min)\cdot (\frac{60\,s}{1\,min} )\cdot (7\,\frac{days}{week} )\cdot (1\,week)$

$m_{bath.week} = 948.205\,lbm$

$m_{others, week} = (62.4\,\frac{lbm}{ft^{3}})\cdot (23\,gal)\cdot (\frac{0.134\,ft^{3}}{1\,gal} )\cdot (7\,\frac{days}{week} )\cdot (1\,week)$

$m_{others, week} = 1346.218\,lbm$

$m_{week} = m_{bath,week} + m_{others, week}$

$m_{week} = 2294.423\,lbm$

The total energy required per week for hot water is:

$Q_{week} = m_{week}\cdot c_{p,water}\cdot \Delta T$

$Q_{week} =(2294.423\,lbm)\cdot (1\,\frac{BTU}{lbm\cdot ^{\textdegree}F} )\cdot (50^{\textdegree}F)$

$Q_{week} = 458884.6\, BTU$

3 0

1 year ago

A baseball of mass m = 0.49 kg is dropped from a height h1 = 2.25 m. It bounces from the concrete below and returns to a final h

Brilliant_brown [7]

Answer:

Explanation:

Impulse = change in momentum

mv - mu , v and u are final and initial velocity during impact at surface

For downward motion of baseball

v² = u² + 2gh₁

= 2 x 9.8 x 2.25

v = 6.64 m / s

It becomes initial velocity during impact .

For body going upwards

v² = u² - 2gh₂

u² = 2 x 9.8 x 1.38

u = 5.2 m / s

This becomes final velocity after impact

change in momentum

m ( final velocity - initial velocity )

.49 ( 5.2 - 6.64 )

= .7056 N.s.

Impulse by floor in upward direction

= .7056 N.s

6 0

2 years ago