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3 years ago

10

Consider a sphere and a cylinder of equal volume made of copper. Both the sphere and the cylinder are initially at the same temp

erature and are exposed to convection in the same environment. Which do you think will cool faster

1 answer:

zepelin [54]3 years ago

7 0

Answer: The cylinder

Explanation:

Among all other solid shapes, the sphere has the smallest area for a given volume.

By experiment, the ratio of the radius of a sphere to a cylinder of equal volume is less than 1.

Recall;

That the Rate of transfer of convective heat (Q) = h × A ×change in temperature.

Where ,

h= the co efficient of convective heat transfer

A= the cross sectional area.

As such, since the sphere has a smaller surface area relative to the cylinder, the sphere transfers heat slower than the cylinder.

Therefore, if the sphere and cylinder are exposed to convection in the same environment, then, the cylinder cools faster.

PS; the more the Area, the higher the rate of heat transfer and vice versa.

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A rocket moves upward, starting from rest with an acceleration of +30.0 m/s2 for 5.00 s. It runs out of fuel at the end of this

olchik [2.2K]

Answer:

The distance covered by the rocket after fuel ran out is $3442.04 m$

Explanation:

Given that the rocket moves with an acceleration $a=30m/s^2$

time $t=5 s$

Since the rocket starts from rest initial velocity $u=0 s$

The distance it travelled within this time is given by $s=ut+ \frac{1}{2} at^2$ $=0 \times 5+ \frac{1}{2} (30\times25)=375 m$

Velocity at this point is given by $v=u+at$

$v=0+30\times5=150m/s$

Given that at this height it runs out of fuel but travels further. Here final velocity $v=0$ (maximum height), initial velocity $u=150 m/s$ and time to zero velocity $t=\frac{v}{g} = \frac{150}{9.8} =15.3 s.$

Thus it travels $15.3 seconds$ more after fuel running out. The distance covered during this period is given

$s= ut+\frac{1}{2} gt^2=150 \times 15.3+1/2 \times9.8 \times 15.3^2=3442.04 m$

7 0

3 years ago

1. What coefficients would balance the following equation?

maksim [4K]

Answer:

D. 4Al + 3O2 → 2Al2O3

Explanation:

Chemical reactions involves the chemical combination of two or more substances called REACTANTS to yield other substances called PRODUCTS. However, in accordance with the LAW OF CONSERVATION OF MASS, the amount of reactants must be equal to that of the products.

To accomplish this, the reaction must be BALANCED. A balanced equation is an equation in which the number of atoms of each element in the reactant side equals the number of atoms in the product side. In this reaction involving Aluminum and Oxygen to give Aluminum oxide as follows:

Al + 02 → Al2O3

A coefficient is used to balance the number of atoms on both sides of the equation as follows:

4Al + 3O2 → 2Al2O3

3 0

3 years ago

Read 2 more answers

You stand on a frictional platform that is rotating at 1.8 rev/s. Your arms are outstretched, and you hold a heavy weight in eac

dusya [7]

Answer:

20.62361 rad/s

489.81804 J

Explanation:

$I_i$ = Initial moment of inertia = 9.3 kgm²

$I_f$ = Final moment of inertia = 5.1 kgm²

$\omega_i$ = Initial angular speed = 1.8 rev/s

$\omega_f$ = Final angular speed

As the angular momentum of the system is conserved

$I_i\omega_i=I_f\omega_f\\\Rightarrow \omega_f=\dfrac{I_i\omega_i}{I_f}\\\Rightarrow \omega_f=\dfrac{9.3\times 1.8}{5.1}\\\Rightarrow \omega_f=3.28235\ rev/s=3.28235\times 2\pi=20.62361\ rad/s$

The resulting angular speed of the platform is 20.62361 rad/s

Change in kinetic energy is given by

$\Delta K=\dfrac{1}{2}(I_f\omega_f^2-I_i\omega_i^2)\\\Rightarrow \Delta K=\dfrac{1}{2}(5.1\times (20.62361)^2-9.3\times (1.8\times 2\pi)^2)\\\Rightarrow \Delta K=489.81804\ J$

The change in kinetic energy of the system is 489.81804 J

As the work was done to move the weight in there was an increase in kinetic energy

6 0

3 years ago

In this dark-colored forest, you started with 50% light moths and 50% dark moths. At the end of your simulation, was there a hig

krek1111 [17]

Dark moths because they use their color to blend in with the trees to hide from birds

5 0

2 years ago

A paintball’s mass is 0.0032kg. A typical paintball strikes a target moving at 85.3 m/s.

vekshin1

Answer:

A) If the paintball stops completely the magnitude of the change in the paintball’s momentum is $p=0.273kg*m/s$

B) If the paintball bounces off its target and afterward moves in the opposite direction with the same speed, the change in the paintball’s momentum is $p=0.546kg*m/s$

C) A paintball bouncing off your skin in the opposite direction with the same speed hurts more than a paintball exploding upon your skin because of the strength exerted is twice than if it explodes.

Explanation:

Hi

A) We use the formula of momentum $p=mv$ , so we have $p=0.0032kg*85.3m/s=0.273kg*m/s$

B) We use the same formula above, then due we have a change of direction at the same speed, therefore the change in the momentum is the double so

$p=2*0.0032kg*85.3m/s=0.546kg*m/s$ .

C) The average strength of the force an object exerts during impact is determined by the amount the object’s momentum changes. therefore

$F=\frac{\Delta p}{\Delta t}$ , as we don't have any data about the impact time but we know momentum is twice, time does no matter and strength is twice too.

4 0

3 years ago