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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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A 80 ohms resistor, 0.2 H inductance and 0.1 mF capacitor are connected in series across a generator (60 Hz, V rms=120 V). Deter
qaws [65]

Answer:

Impedance = 93.75 ohms

Current = 1.81 A

Explanation:

Resistance = R = 80 ohms

Inductance = L = 0.2 H

Inductive reactance = XL = X_{L}= = ωL = (2πf) L

= 2 (3.14) (60)(0.2) = 75.398 Ohms

Capacitive reactance = 1 / ωC = 1/(2πf)C = 1 / [(2π)(60)(0.1 × 10⁻3)]

= 26.526 Ohms  

Impedance = Z = \sqrt{R^{2} + (X_{L} - X_{C})^{^{2}}} =

= \sqrt{8788.511} = 93.747 ohms  

Voltage = \sqrt{2} × 120 = 169.7056 V

Current = I = V ÷ R = (169.7056) ÷ 93,747 = 1.81 A

8 0
3 years ago
The force of replusion between two like charged particles will increase if​
Alex_Xolod [135]

Answer:

The distance of separation is decreased

Explanation:

From Cuolomb's law, we know that the strength of charge is inversely proportional to the distance of separation between the charges. To mean that increasing the distance let's say from 2m to 3 m would mean initial strength getting form 1/4 to 1/9 which is a decrease. The vice versa is true hence the force of repulsion can increase only when we decrease the distance of separation.

7 0
3 years ago
An airplane is moving at 350 km/hr. If a bomb is
Molodets [167]

Answers:

a) -171.402 m/s

b) 17.49 s

c) 1700.99 m

Explanation:

We can solve this problem with the following equations:

y=y_{o}+V_{oy}t-\frac{1}{2}gt^{2} (1)

x=V_{ox}t (2)

V_{f}=V_{oy}-gt (3)

Where:

y=0 m is the bomb's final jeight

y_{o}=1.5 km \frac{1000 m}{1 km}=1500 m is the bomb'e initial height

V_{oy}=0 m/s is the bomb's initial vertical velocity, since the airplane was moving horizontally

t is the time

g=9.8 m/s^{2} is the acceleration due gravity

x is the bomb's range

V_{ox}=350 \frac{km}{h} \frac{1000 m}{1 km} \frac{1 h}{3600 s}=97.22 m/s is the bomb's initial horizontal velocity

V_{f} is the bomb's fina velocity

Knowing this, let's begin with the answers:

<h3>b) Time</h3>

With the conditions given above, equation (1) is now written as:

y_{o}=\frac{1}{2}gt^{2} (4)

Isolating t:

t=\sqrt{\frac{2 y_{o}}{g}} (5)

t=\sqrt{\frac{2 (1500 m)}{9.8 m/s^{2}}} (6)

t=17.49 s (7)

<h3>a) Final velocity</h3>

Since V_{oy}=0 m/s, equation (3) is written as:

V_{f}=-gt (8)

V_{f}=-(97.22)(17.49 s) (9)

V_{f}=-171.402 m/s (10) The negative sign ony indicates the direction is downwards

<h3>c) Range</h3>

Substituting (7) in (2):

x=(97.22 m/s)(17.49 s) (11)

x=1700.99 m (12)

5 0
3 years ago
Distinguish
yaroslaw [1]

Answer:

Velocity and speed both are continuously increasing.

Acceleration is constant.

Explanation:

Speed is defined as length of path covered by a body per unit time. Speed is a scalar quantity that consist of magnitude only and not direction.

Velocity is defined as the displacement per unit times. Displacement is the shortest distance between the two points. It is a vector quantity and  hence has a direction in the direction of displacement along with its own magnitude.

  • Both velocity and speed have same unit of measure which is meter per second in S.I. During <em>free fall</em> in the absence of any air resistance the velocity and speed both will be having a vertical downward direction with continuously increasing magnitude. Tough we are not concerned about the direction when discussing about speed but here both are equal since the motion is linear.

Acceleration is the rate of change in velocity of a body which is a vector quantity. For speed we are concerned about instantaneous acceleration since for a short period of time it may have a specific direction.

  • During free fall the acceleration is of a body is equal to the acceleration due to gravity and constant when the height of fall is much lesser than the radius of the earth.
4 0
3 years ago
12. A car is travelling at 30 m/s when the driver sees a red light in the distance and immediately applies the brakes. The car c
Triss [41]

Answer:

22.5 m

Explanation:

From the question given above, the following data were obtained:

Initial velocity (u) = 30 m/s

Time (t) = 1.5 s

Final velocity (v) = 0 m/s

Distance (s) =?

The distance to which the car move before stopping from the time the driver applied the brake can be obtained as follow:

s = (u + v)t/2

s = (30 + 0)1.5 / 2

s = (30 × 1.5) / 2

s = 45 / 2

s = 22.5 m

Thus, the car will move to a distance of 22.5 m before stopping from the time the driver applied the brake.

4 0
3 years ago
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