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Novosadov [1.4K]
3 years ago
13

Two identical twins hold on to a rope, one at each end, on a smooth, frictionless ice surface. They skate in a circle about the

center of the rope (the center of mass of the two-body system) and perpendicular to the ice. The mass of each twin is 78.0 kg. The rope of negligible mass is 4.0 m long and they move at a speed of 4.30 m/s.
(a) What is the magnitude, in kg · m2/s, of the angular momentum of the system comprised of the two twins?
___________kg · m2/s.
(b) They now pull on the rope and move closer to each other so that the rope between them is now half as long. Determine the speed, in m/s, with which they move now.
__________m/s.
(c) The two twins have to do work in order to move closer to each other. How much work, in joules, did they do?
____________J.
Physics
1 answer:
777dan777 [17]3 years ago
5 0

Answer:

Part a)

L = 2683.2 kg m^2/s

Part b)

v' = 8.60 m/s

Part c)

W = 4326.7 J

Explanation:

Part a)

As we know that there is no external torque on the system of two twins

so here we will use

L = mv r + mvr

L = 2(78 \times 4.30 \times 4)

L = 2683.2 kg m^2/s

Part b)

Since angular momentum is conserved here as there is no external torque

so we will have

2(m v r) = 2( m v' \frac{r}{2})

v' = 2v

v' = 8.60 m/s

Part c)

Work done by both of them = change in kinetic energy

so we have

W = 2(\frac{1}{2}mv'^2 - \frac{1}{2}mv^2)

W = m(v'^2 - v^2)

W = 78(8.60^2 - 4.3^2)

W = 4326.7 J

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A vector quantity must include both magnitude and direction. Which measurement is a vector quantity? A) the rain accumulation at
bogdanovich [222]

Answer:

B)The motion of water in an ocean current

Explanation:

With respect to measurements, a vector has both a magnitude and a direction. The first three examples (maximum height of a hill, air temperature, and rain accumulation) are magnitudes only. The fourth example (motion of water in an ocean current) is a vector, because it has a magnitude (speed) and a direction (with the current).

4 0
3 years ago
At 19 ºC a volume of air takes us 9.0 mL in an expandable container. What is its volume after it is heated up to 50. ºC?
Katena32 [7]
According to Charles law, we know, at constant pressure, volume is directly proportional to temperature. 
So, <span>V/T = constant 
</span>
V₁/t₁ = V₂/t₂
V₁t₂ = V₂t₁

Here, we have: V₁ = 9 mL
V₂ = ?
T₂ = 50+272 = 323 K
T₁ = 19+273 = 292 K

Substitute their values into the expression:
9 × 323 = V₂ × 292
V₂ = 2907 / 292
V₂ = 9.95
After rounding-off to unit place value, it would be equal to 10 mL

So, In short Option C would be your correct answer.

Hope this helps!
5 0
3 years ago
Consider a 20 cm thick granite wall with a thermal conductivity of 2.79 W/m·K. The temperature of the left surface is held const
kozerog [31]

Answer:

The right wall surface temperature and heat flux through the wall is 35.5°C and 202.3W/m²

Explanation:

Thickness of the wall is  L=  20cm = 0.2m

Thermal conductivity of the wall is  K = 2.79 W/m·K

Temperature at the left side surface is T₁ =  50°C

Temperature of the air is T = 22°C

Convection heat transfer coefficient is  h = 15 W/m2·K

Heat conduction process through wall is equal to the heat convection process so

Q_{conduction} = Q_{convection}

Expression for the heat conduction process is

Q_{conduction} = \frac{K(T_1 - T)}{L}

Expression for the heat convection process is

Q_{convection} = h(T_2 - T)

Substitute the expressions of conduction and convection in equation above

Q_{conduction} = Q_{convection}

\frac{K(T_1 - T_2)}{L} = h(T_2 - T)

Substitute the values in above equation

\frac{2.79(50- T_2)}{0.2} = 15(T_2 - 22)\\\\T_2 = 35.5^\circC

Now heat flux through the wall can be calculated as

q_{flux} = Q_{conduction} \\\\q_{flux}  = \frac{K(T_1 - T_2)}{L}\\\\q_{flux}  = \frac{2.79(50 - 35.5)}{0.2}\\\\q_{flux} = 202.3W/m^2

Thus, the right wall surface temperature and heat flux through the wall is 35.5°C and 202.3W/m²

6 0
3 years ago
Describe the shape of a convex lens and explain what it does to light.
alexira [117]
Convex lenses are thicker at the centers than the edges, they are known as the converging lenses. Rays of light that pass through the lens are brought closer together (they converge). When rays of light that are parallel pass through a convex lens they are refracted, the refracted rays converge at one point called the principal focus. 
4 0
3 years ago
A chemical reaction takes place in which energy is absorbed. Arrange the characteristics of the reaction in order from start to
Ira Lisetskai [31]
<h2>Answer</h2>

It will be single step endothermic reaction.

<h2>Expalantion</h2>

In the endothermic reaction, the reactants come together to convert to products by absorbing the heat from the external source. This reaction is explained is also known as one step reaction as reactants meet to get the transition stage and converts to the product. But in some reactions, the activation energy required to activate the reactants to get the transition stage to form products. For this, the reaction will have the steps as activation energy, reactant meet, transition stage and products form.

6 0
3 years ago
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