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inna [77]
3 years ago
7

Two kids create a makeshift seesaw by setting a 4-m long uniform plank on a saw horse. The saw horse is 0.5 m to the left of the

center of mass of the plank. The child of mass m1 = 42 kg sits at the left end of the plank. The child of mass m2 = 31 kg sits 1 m to the right of the center of mass of the plank. What is the mass of the plank?
Physics
1 answer:
GREYUIT [131]3 years ago
3 0

Answer:

The mass of the plank is 33 kg.

Explanation:

Given that,

Length of plank = 4 m

Distance in left from the center= 0.5 m

Mass of child = 42 kg

Mass of other child = 31 kg

Distance in right from the center= 1 m

We can sum torques around the saw horse; each force generates a torque equal to force x distance from saw horse

We need to calculate the torque for first child

Using formula of torque

\tau =mg\times d

Put the value into the formula

\tau=42\times9.8\times1.5

\tau=617.4\ N-m

We need to calculate the torque for second child

The child is 1.5 m from the saw horse

Using formula of torque

\tau' =mg\times d

Put the value into the formula

\tau'=31\times9.8\times1.5

\tau'=455.7\ N-m

The weight of the plank produces a clockwise torque

\tau''=mg\times d

\tau''=mg\times 0.5

We need to calculate the mass of the plank

Using balance equation of torque

\tau=\tau''+\tau'

Put the value into the formula

617.4=mg\times0.5+455.7

m=\dfrac{617.4-455.7}{0.5\times9.8}

m=33\ kg

Hence, The mass of the plank is 33 kg.

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Bess [88]

Answer:

Magnetic fields can be used to make electricity

Moving a magnet around a coil of wire, or moving a coil of wire around a magnet, pushes the electrons in the wire and creates an electrical current. Electricity generators essentially convert kinetic energy (the energy of motion) into electrical energy

Explanation:

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3 years ago
Does aluminum foil refract light? Why?
nikitadnepr [17]

yes it does it because the material cause it to refract and the stronger it is the more it will refract

4 0
3 years ago
The length of a simple pendulum is 0.66 m, the pendulum bob has a mass of 310 grams, and it is released at an angle of 12 degree
lina2011 [118]
A) the periodic time is given by the equation;
 T= 2π√(L/g)
For the frequency will be obtained by 1/T (Hz)
T = 2 × 3.14 √ (0.66/9.81)
   = 6.28 × √0.0673
    = 1.6289 Seconds
Frequency = 1/T = f = 1/1.6289
 thus; frequency = 0.614 Hz

b)  The vertical distance, the height is given by
 h= 0.66 cos 12
 h = 0.65 m
Vertical fall at the lowest point = 0.66 - 0.65 = 0.01 m
Applying conservation of energy
energy lost (MgΔh) = KE gained (1/2mv²)
 mgh = 1/2mv²
  v² = 2gΔh = 2×9.81 × 0.01 
                   = 0.1962
v = 0.443 m/s

c) total energy = KE + GPE = KE when GPE is equal to zero (at the lowest point possible)
Thus total energy is equal to;
E = 1/2mv²
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4 0
3 years ago
A gas, behaving ideally, has a pressure P1 and at a volume V1. The pressure of the gas is changed to P2. Using Avogadro’s, Charl
Bond [772]

Answer:

Boyle's Law

\therefore P_1.V_1=P_2.V_2

Explanation:

Given that:

<u><em>initially:</em></u>

pressure of gas, = P_1

volume of gas, = V_1

<em><u>finally:</u></em>

pressure of gas, = P_2

volume of gas, = V_2

<u>To solve for final volume</u> V_2

<em>According to Avogadro’s law the volume of an ideal gas is directly proportional to the no. of moles of the gas under a constant temperature and pressure.</em>

<em>According to the Charles' law, at constant pressure the volume of a given mass of an ideal gas is directly proportional to its temperature.</em>

But here we have a change in the pressure of the Gas so we cannot apply Avogadro’s law and Charles' law.

Here nothing is said about the temperature, so we consider the Boyle's Law which states that <em>at constant temperature the volume of a given mass of an ideal gas is inversely proportional to its pressure.</em>

Mathematically:

P_1\propto \frac{1}{V_1}

\Rightarrow P_1.V_1=k\ \rm(constant)

\therefore P_1.V_1=P_2.V_2

5 0
3 years ago
The temperature and time t given in hours from 0 to 24 after midnight in downtown mathville is given by t=10-5 sin(pi/12 t) degr
Dvinal [7]

Answer:

T_A_v_g=9.918192559$^{\circ}C

Explanation:

The problem tell us that the temperature as function of time in downtown mathville is given by:

T(t)=10-5*sin(\frac{\pi}{12t})

The average temperature over a given interval can be calculated as:

T_a_v_g=\frac{T_o+T_f}{2}

Where:

T_o=Initial\hspace{3}temperature\\T_f=Final\hspace{3}temperature

So, the initial temperature in this case, would be the temperature at noon, and the final temperature would be the temperature at midnight:

Therefore:

T_o=T(12)=10-5*sin(\frac{\pi}{12*12}) =9.890925575$^{\circ}C

T_f=T(24)=10-5*sin(\frac{\pi}{12*24}) =9.945459543$^{\circ}C

Hence, the average temperature between noon and midnight is:

T_A_v_g=\frac{9.890925575+9.945459543}{2}=9.918192559$^{\circ}C

3 0
3 years ago
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