What is 20kg x 9.8m/s2

In braking an automobile, the friction between the brake drums and brake shoes converts the car's kinetic energy into heat. If a

satela [25.4K]

To solve this problem it is necessary to apply the concepts related to energy conservation.

In this case the kinetic energy is given as

$KE = \frac{1}{2} mv^2$

Where,

m = mass

v= Velocity

In the case of heat lost energy (for all 4 wheels) we have to

$Q = mC_p \Delta T \rightarrow 4Q = 4mC_p \Delta T$

m = mass

$C_p =$ Specific Heat

$\Delta T$ = Change at temperature

For conservation we have to

$KE = Q$

$\frac{1}{2} mv^2 = 4mC_p \Delta T$

$\Delta T = \frac{1}{2}\frac{mv^2}{4mC_p}$

$\Delta T = \frac{1}{2}\frac{(1500)(30)^2}{4(8)(448)}$

$\Delta T = 47.084\°C \approx 47\°C$

Therefore the temperature rises in each of the four brake drums around to 47°C

4 0

3 years ago

In August 2011, the Juno spacecraft was launched from Earth with the mission of orbiting Jupiter in 2016. The closest distance b

Vikentia [17]

(a) 8927 mi/h

In order to calculate the average speed, we need to convert the time (t=5.0 y) into hours first. In 1 year, we have 365 days, each day consisting of 24 hours, so the time taken is:

$t=(5.0 y)(365 d/y)(24 h/d)=43,800 h$

The distance covered by the spacecraft is

$d=391 mil. mi = 391\cdot 10^6 mi$

Therefore, the average speed is just the ratio between the distance covered and the time taken:

$v=\frac{d}{t}=\frac{391\cdot 10^6 mi}{43,800 h}=8,927 mi/h$

(b) 35 minutes (2097 seconds)

The transmitted signals (which is a radio wave, which is an electromagnetic wave) travels back to the Earth at the speed of light:

$c=3.0\cdot 10^8 m/s$

Since 1 miles = 1609 metres, the distance covered by the signal is

$d=391\cdot 10^6 mi \cdot (1609 m/mi)=6.29\cdot 10^{11} m$

So, the time taken by the signal will be

$t=\frac{d}{v}=\frac{6.29\cdot 10^{11} m}{3.0\cdot 10^8 m/s}=2097 s$

And since 1 minute = 60 sec, the time taken is

$t=2097 s \cdot \frac{1}{60 s/min}\sim 35 min$

7 0

3 years ago

A tourist stands at the top of the Grand Canyon, holding a rock, overlooking the valley below. Find the final velocity, and disp

uranmaximum [27]

Answer:

a. Vf = 39.24 [m/s]

b. Vf = 31.24 [m/s]

c. Vf = 47.24 [m/s].

Explanation:

To solve this problem we can use the following equation of kinematics. We have to keep in mind that the gravitational acceleration acts downwards, therefore when the rock falls towards the abyss it has the same direction of the acceleration and that is why the gravitational acceleration has a positive sign in the equation.

$v_{f}=v_{o}+g*t$

where:

Vf = final velocity [m/s]

Vo = initial velocity = 0 (when the rock is dropped)

g = gravitational acceleration = 9.81 [m/s²]

t = time = 4 [s]

a.

$v_{f}=0+9.81*4\\v_{f}= 39.24 [m/s]$

b.

In this particular situation, the acceleration will be taken as negative because the gravity is pointing in the opposite direction of the movement of the rock.

$v_{f}=8-(9.81*4)\\v_{f}=-31.24[m/s]$

The negative sign in the answer tells us that the rock no longer moves up instead it does downwards when 4 seconds have passed.

c.

$v_{f}=8+(9.81*4)\\v_{f}=47.24[m/s]$

4 0

3 years ago

body starting from rest and moving with an uniform acceleration of 3 m/s²..What is its velocity after 15s?

Luba_88 [7]

<h2>Answer :</h2>

□ The Final velocity of body = 45 m/s $\sf{ }$

<h2>Given :</h2>

Initial velocity of body = 0 m/s

Acceleration of body = 3 m/s²

Time taken by body = 15 sec

<h2>To Calculate :</h2>

Final velocity of body = ?

<h2>How To Calculate ?</h2>

Here in this question we are provided that a body is in rest so it's initial velocity will be 0 m/s (because from rest), Acceleration of body is 3 m/s², and Time taken is also given which is 15 sec.

To calculate the Final velocity of body we'll use the first equation of motion which says v = u + at

Where,

v is the Final velocity in m/s.

u is the Initial velocity in m/s.

a is the Acceleration in m/s².

t is the Time taken in second.

<h2>Calculation :</h2>

From first equation of motion

⇒ v = u + at

⇒ v = 0 + 3 × 15

⇒ v = 0 + 45

⇒ v = 45

Hence, the Final velocity of body is 45 m/s.

7 0

3 years ago

Read 2 more answers

When two things are the same temperature:

Rus_ich [418]

Answer:

its obviously D if all the other says "incorrect answer" XD

Explanation:

4 0

3 years ago