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4 years ago

O Which is true? (Check all that apply)

1 answer:

6 0

Let's see:

<span> Objects with more mass require more force to move them. --> true, in fact Newtons's second law states:
F=ma
so, the larger the mass m, the larger the force F needed to move the object with same acceleration a

 Objects that experience balanced forces CANNOT be moving.--> false, in fact, when the resultant of the forces acting on the object is zero (so, all the forces are balanced), it means the object has no acceleration. However, this doesn't imply that the velocity of the object is zero, so it is possible that the object is moving even if all the forces are are balanced

 Objects that are in motion require an unbalanced force to stop them. --> true: in fact, if the forces acting on the object are balanced, then for Newton's second law
F=ma
the acceleration of the object would be zero, so the object would still move by uniform motion. So, in order to stop the object, we need unbalanced forces acting on it.

 The acceleration of an object would increase if there is an increase in the force on the object. --> true: in fact, Newton's second law states
F=ma
so, if the force F on the object increases, then the acceleration a of the object increases as well.</span>

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Two castings are proposed for a study. One casting is a cube 10.16 cm (4 in.) on a side; the other is a rectangle 10.64 cm (16 i

iren [92.7K]

To solve the problem it is necessary to apply the concepts related to Chvorinov's Law, which states that

$\frac{T_r}{T_c} = (\frac{V_r}{V_c}*\frac{SA_c}{SA_r})^2$

Where,

$V_c$ = Volume cube

$SA_c$ = Superficial Area from Cube

$V_r$ = Volume Rectangle

$SA_r$ = Superficial Area from Rectangle

Our values are given as (I will try to develop the problem in English units for ease of calculations),

$V_c = 4^3 = 64in^3$

$SA_c = 6*4^2=96in^2$

$SA_r = 2*(1*16+4*1+16*4)=168in^2$

$V_r = 4*1*16 = 64in^3$

Applying the Chvorinov equation we have to,

$\frac{T_r}{T_c} = (\frac{V_r}{V_c}*\frac{SA_c}{SA_r})^2$

$\frac{T_r}{T_c} = (\frac{64}{64}*\frac{96}{168})^2$

$\frac{T_r}{T_c} = (\frac{96}{168})^2$

$\frac{T_r}{T_c} = 0.3265$

The stipulated time for the cube is 14.5 then,

$T_r = 0.3265*14.5$

$T_r = 4.735min$

4 0

4 years ago

A plane travels at a speed of 205mph in still air. Flying with a tailwind, the plane is clocked over a distance of 1000 miles. F

vaieri [72.5K]

While plane is moving under tailwind condition it took time "t"

so here we will have

$t = \frac{d}{v_{net}}$

here net speed of the plane will be given as

$v_{net} = v + v_w$

$t = \frac{1000}{205 + v_w}$

similarly when it moves under the condition of headwind its net speed is given as

$v_{net} = v - v_w$

now time taken to cover the distance is 2 hours more

$t + 2 = \frac{1000}{205 - v_w}$

now solving two equations

$\frac{1000}{205 + v_w} + 2 = \frac{1000}{205 - v_w}$

solving above for v_w we got

$v_w = 40.4 mph$

6 0

3 years ago

Two immersion heaters, A and B, are both connected to a 120.0-V supply. Heater A can raise the temperature of 1.00 L of water fr

Inessa05 [86]

Answer:

Ratio of resistance of heater A to resistance of heater B is 5.80

Explanation:

Consider C be the specific heat of water, R₁ and R₂ be the resistance of heater A and heater B respectively.

Given:

Mass of water in heater A, m₁ = 1 L

Mass of water in heater B, m₂ = 5.80 L

Initial temperature, T₀ = 20 ⁰C

Final temperature, T₁ = 90 ⁰C

Time, t = 5 min

Amount of heat required to raise the temperature of water by heaters A and B are given by:

Q₁ = m₁C(T₁ - T₀) and

Q₂ = m₂C(T₁ - T₀)

Ratio of power used by both the heaters A and B is:

$\frac{P_{1} }{P_{2} } =\frac{Q_{1} }{t} \times\frac{t}{Q_{2} }$

Since, time t, temperature difference(T₁ - T₀) and specific heat C are same for both the heaters A and B. So, the above equation becomes:

$\frac{P_{1} }{P_{2} } =\frac{m_{1} }{m_{2} }$ ...(1)

The relation to determine electrical power for both heaters A and B are:

$P_{1}=\frac{V^{2} }{R_{1} }$ and

$P_{2}=\frac{V^{2} }{R_{2} }$

Here V is the voltage applied to both the heaters and is equal.

So, the ratio of electrical power of heaters is:

$\frac{P_{1} }{P_{2} } =\frac{R_{2} }{R_{1} }$ ....(2)

But according to the problem, the electrical power is converted into the thermal power. So,equation (1) and (2) are equal. Hence,

$\frac{m_{1} }{m_{2} } =\frac{R_{2} }{R_{1} }$

Substitute the suitable values in the above equation.

$\frac{1 }{5.80 } =\frac{R_{2} }{R_{1} }$

$\frac{R_{1} }{R_{2} }=5.80$

6 0

3 years ago

There are four springs stretched by the same mass.

kirill115 [55]

Answer:

That would be Spring C

Explanation:

i took the test :P

6 0

4 years ago

When we turn on a switch it helps complete the electric circuit and the current passes from the positive to the negative in the

Schach [20]

Answer:

We don't get shocked because of the type of materials used in the switch is a poor conductor of electricity

Explanation:

Yes it is quite amazing we don't get shocked, this is because of resistance of the type of materials used in the switch (non conductors of electricity) so that when you try to put on a switch no current passes through you, mostly the material are made from plastics Or ceramics which are actually poor conductors of electricity.

5 0

3 years ago