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leva [86]
3 years ago
7

The star Betelgeuse is about 600 light-years away. If it explodes tonight,

Physics
2 answers:
lana [24]3 years ago
6 0

The star Betelgeuse is about 600 light-years away.

If it explodes tonight, we won't know about it until 600 years from now. <em>(C)</em>

(Maybe it already has.  If it exploded any time after the year 1419, we have no way to know it yet.)

Thepotemich [5.8K]3 years ago
4 0

Answer:

C

Explanation:

It has to travel 600 light years before we would be able to observe the explosion.

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A certain 100W light bulb has an efficiency of 95%. How much thermal energy will this light bulb add to the inside of a room in
Usimov [2.4K]
Since the bulb consumes 100 watts of power and its efficiency is 95%,
it generates 95 watts of light energy and 5 watts of heat energy whenever
it's turned on.

5 watts means  5 joules of energy per second.

(2.5 hours) x (3,600 seconds/hour) =  9,000 seconds

(9,000 seconds) x (5 joules/second)  =  45,000 joules of heat in 2.5 hours

7 0
3 years ago
A 2.7-kg block is released from rest and allowed to slide down a frictionless surface and into a spring. The far end of the spri
exis [7]

a) The speed of the block at a height of 0.25 m is 2.38 m/s

b) The compression of the spring is 0.25 m

c) The final height of the block is 0.54 m

Explanation:

a)

We can solve the problem by using the law of conservation of energy. In fact, the total mechanical energy (sum of kinetic+gravitational potential energy) must be conserved in absence of friction. So we can write:

U_i +K_i = U_f + K_f

where

U_i is the initial potential energy, at the top

K_i is the initial kinetic energy, at the top

U_f is the final potential energy, at halfway

K_f is the final kinetic energy, at halfway

The equation can be rewritten as

mgh_i + \frac{1}{2}mu^2 = mgh_f + \frac{1}{2}mv^2

where:

m = 2.7 kg is the mass of the block

g=9.8 m/s^2 is the acceleration of gravity

h_i = 0.54 is the initial height

u = 0 is the initial speed

h_f = 0.25 m is the final height of the block

v is the final speed when the block is at a height of 0.25 m

Solving for v,

v=\sqrt{u^2+2g(h_i-h_f)}=\sqrt{0+2(9.8)(0.54-0.25)}=2.38 m/s

b)

The total mechanical energy of the block can be calculated from the initial conditions, and it is

E=K_i + U_i = 0 + mgh_i = (2.7)(9.8)(0.54)=14.3 J

At the bottom of the ramp, the gravitational potential energy has become zero (because the final heigth is zero), and all the energy has been converted into kinetic energy. However, then the block compresses the spring, and the maximum compression of the spring occurs when the block stops: at that moment, all the energy of the block has been converted into elastic potential energy of the spring. So we can write

E=E_e = \frac{1}{2}kx^2

where

k = 453 N/m is the spring constant

x is the compression of the spring

And solving for x, we find

x=\sqrt{\frac{2E}{k}}=\sqrt{\frac{2(14.3)}{453}}=0.25 m

c)

If there is no friction acting on the block, we can apply again the law of conservation of energy. This time, the initial energy is the elastic potential energy stored in the spring:

E=E_e = 14.3 J

while the final energy is the energy at the point of maximum height, where all the energy has been converted into gravitational potetial energy:

E=U_f = mg h_f

where h_f is the maximum height reached. Solving for this quantity, we find

h_f = \frac{E}{mg}=\frac{14.3}{(2.7)(9.8)}=0.54 m

which is the initial height: this is correct, because the total mechanical energy is conserved, so the block must return to its initial position.

Learn more about kinetic and potential energy:

brainly.com/question/1198647

brainly.com/question/10770261

brainly.com/question/6536722

#LearnwithBrainly

5 0
3 years ago
The ideal mechanical advantage of an inclined plane is 3.5, and its efficiency is 0.6. What is the mechanical advantage of the i
Nadya [2.5K]
Mechanical advantage = ideal mechanical advantage x efficiency = 3.5 x 0.6 = 2.1
The mechanical advantage of the inclined plane is 2.1

7 0
3 years ago
What is inertia?by Walter Levin..<br>​
Tom [10]

Inertia is directly proportional to mass.

What is Walter Lewin famous for?

Walter Hendrik Gustav Lewin (born January 29, 1936) is a Dutch astrophysicist and former professor of physics at the Massachusetts Institute of Technology.

Lewin earned his doctorate in nuclear physics in 1965 at the Delft University of Technology and was a member of MIT's physics faculty for 43 years beginning in 1966 until his retirement in 2009.

According to Walter Levin,

The concept of moment of inertia is demonstrated by rolling a series of cylinders down an inclined plane.

Inertia is the resistance of any physical object to a change in its velocity. This includes changes to the object's speed, or direction of motion. An aspect of this property is the tendency of objects to keep moving in a straight line at a constant speed when no forces act upon them.

By rolling a series of cylinders down on an inclined plane , he demonstrated that a cylinder have a smooth friction.

He compares the rolling cylinder by using hollow cylinder and a heavy cylinder , and finalize the result that a hollow cylinder moves slowly but the heavy cylinder move faster.

Hence , By doing this experiment he explained about the inertia that Inertia depend on the mass of the object. As the heavy the object it will take more time to travel or move.

Learn more about inertia here:brainly.com/question/3268780

#SPJ1

7 0
1 year ago
How do you solve for frequency?
AleksAgata [21]

Answer:

frequency= 1/time period

5 0
3 years ago
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