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Maurinko [17]
3 years ago
7

A 750-kg car moving at 23 m/s brakes to a stop. Assume that all the kinetic energy is transformed into thermal energy. The brake

s contain about 15 kg of iron, which absorbs the energy. What is the increase in temperature of the brakes?
Physics
1 answer:
ahrayia [7]3 years ago
7 0

Answer:

The temperature of the brakes is 29.38°C.

Explanation:

Given that,

Mass of car = 750 kg

Speed = 23 m/s

Mass of iron = 15 kg

We need to calculate the kinetic energy of car

Using formula of kinetic energy

K.E=\dfrac{1}{2}mv^2

K.E=\dfrac{1}{2}\times750\times23^2

K.E=198.375\ kJ

We need to calculate the temperature of the brakes

Using formula of energy

K.E=mc\Delta T

Put the value into the formula

198.375=15\times0.450\times\Delta T

\Delta T=\dfrac{198.375}{15\times0.450}

\Delta T=29.38^{\circ}C

Hence, The temperature of the brakes is 29.38°C.

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Explanation:

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mass defect = 56.936296 + .00055 - 56.935399

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3 years ago
A certain tuning fork vibrates at a frequency of 215 Hz while each tip of its two prongs has an amplitude of 0.832 mm. (a) What
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Explanation:

It is given that,

Frequency of vibration, f = 215 Hz

Amplitude, A = 0.832 mm

(a) Let T is the period of this motion. It is given by the following relation as :

T=\dfrac{1}{f}

T=\dfrac{1}{215}

T=4.65\times 10^{-3}\ s

(b) Speed of sound in air, v = 343 m/s

It can be given by :

v=f\times \lambda

\lambda=\dfrac{v}{f}

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3 years ago
The current theory of the structure of the
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Answers:

a) 2.82(10)^{21} kg

b) 1410 J

c) 36.62 m/s

Explanation:

<h3>a) Mass of the continent</h3>

Density \rho  is defined as a relation between mass m and volume V:

\rho=\frac{m}{V} (1)

Where:

\rho=2720 kg/m^{3} is the average density of the continent

m is the mass of the continent

V is the volume of the continent, which can be estimated is we assume it as a a slab of rock 5300 km on a side and 37 km deep:

V=(length)(width)(depth)=(5300 km)(5300 km)(37 km)=1,030,330,000 km^{3} \frac{(1000 m)^{3}}{1 km^{3}}=1.03933(10)^{18} m^{3}

Finding the mass:

m=\rho V (2)

m=(2720 kg/m^{3})(1.03933(10)^{18} m^{3}) (3)

m=2.82(10)^{21} kg (4) This is the mass of the continent

<h3>b) Kinetic energy of the continent</h3>

Kinetic energy K is given by the following equation:

K=\frac{1}{2}mv^{2} (5)

Where:

m=2.82(10)^{21} kg is the mass of the continent

v=4.8 \frac{cm}{year} \frac{1 m}{100 cm} \frac{1 year}{365 days} \frac{1 day}{24 hours} \frac{1 hour}{3600 s}=1(10)^{-9} m/s is the velocity of the continent

K=\frac{1}{2}(2.82(10)^{21} kg)(1(10)^{-9} m/s)^{2} (6)

K=1410 J (7) This is the kinetic energy of the continent

<h3>c) Speed of the jogger</h3>

If we have a jogger with mass m=77 kg and the same kinetic energy as that of the continent 1413 J, we can find its velocity by isolating v from (5):

v=\sqrt{\frac{2 K}{m}} (6)

v=\sqrt{\frac{2 (1413 J)}{77 kg}}

Finally:

v=36.62 m/s This is the speed of the jogger

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