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Andrej [43]
3 years ago
9

When you rub a match against a rough surface, fire results, giving off light and heat. The law of conservation of energy says th

at energy cannot be created.
How can you explain the fire seeming to come from nowhere?

The energy was stored in chemical bonds before it became heat and light.
Matches are made to take up energy from surfaces.
The energy started out as the sound energy of the rubbing match.
Physics
2 answers:
Trava [24]3 years ago
7 0
The law of conservation of energy states that energy can neither be created nor destroyed. striking a match stick with a surface that conducts heat, it is not part of the law
shutvik [7]3 years ago
4 0
The energy was stored in chemical bonds before it became heat and light, it is the result when you rub a match against a rough surface. Energy can not be created nor destroyed but it can be stored, potential energy is stored in a match when you strike it, it releases that energy.
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A stone is thrown horizontally with an initial speed of 10 m/s from the edge of a cliff. A stopwatch measures the stone's trajec
olga2289 [7]

Answer:

The height of the cliff is 90.60 meters.

Explanation:

It is given that,

Initial horizontal speed of the stone, u = 10 m/s

Initial vertical speed of the stone, u' = 0 (as there is no motion in vertical direction)

The time taken by the stone from the top of the cliff to the bottom to be 4.3 s, t = 4.3 s

Let h is the height of the cliff. Using the second equation of motion in vertical direction to find it. It is given by :

h=u't+\dfrac{1}{2}gt^2

h=\dfrac{1}{2}gt^2

h=\dfrac{1}{2}\times 9.8\times (4.3)^2

h = 90.60 meters

So, the height of the cliff is 90.60 meters. Hence, this is the required solution.

5 0
3 years ago
Back in their laboratory, the team of scientists carefully measure the changes in density of a freshwater sample as they decreas
BabaBlast [244]

Answer: As the temperature of the water decreases from 20 degrees celsius to 4 degrees celsius, the density increases.

Explanation:

7 0
2 years ago
Read 2 more answers
A 2.5-kg ball and a 5.0-kg ball have an elastic collision. Before the collision, the 2.5-kg ball was at rest and the other ball
lesantik [10]

The kinetic energy of 2.5 kg ball after collision is 27.09 J.

Answer:

Explanation:

In elastic collision, the sum of momentum of the objects before collision will be equal to the sum of momentum of the objects after collision.  

We know that momentum is the product of mass and velocity acting on any object.

So, the conservation of energy in elastic collision leads to following equation:

M_{1} u_{1} +M_{2} u_{2}=M_{1}  v_{1}+M_{2}  v_{2}

Since, the momentum is conserved ,the kinetic energy will also be conserved in elastic collision. So

M_{1} u_{1} ^{2}+M_{2} u_{2} ^{2}=M_{1}v_{1} ^{2}+  M_{2}v_{2} ^{2}

Since initial velocity for M1 ball is zero, then

M_{2} u_{2}=M_{1}  v_{1}+M_{2}  v_{2}

and

M_{2} u_{2} ^{2}=M_{1}v_{1} ^{2}+  M_{2}v_{2} ^{2}

So, on solving all the above equation, we get an equation for velocity and that is

\frac{2M_{2}u_{2} }{(M_{1}+M_{2}  }=final velocity of ball with mass 2.5 kg

v = \frac{2(5*3.5)}{2.5+5}=4.67 m/s

So kinetic energy will be 1/2 mv2

Kinetic energy of 2.5 kg ball is \frac{1}{2}*2.5*(4.67)^{2}  =27.09 J

So the kinetic energy of 2.5 kg ball after collision is 27.09 J.

6 0
3 years ago
A simple pendulum of length of 1.37 m and mass of 6.66 kg is given an initial speed of 2.85 m/s at its equilibrium position. Det
yawa3891 [41]

Answer:

2.35 s

Explanation:

The period of a simple pendulum is expressed as;

                                T = 2π\sqrt{\frac{L}{g} }

Where

T is the period in seconds

L is the length in metres

g is acceleration due to gravity

                                 T = 2π\sqrt{\frac{1.37}{9.8}}

                                 T = 2.349 s

                                 T = 2.35 s

8 0
3 years ago
The question on science please answer correctly
umka2103 [35]
The 5kg object 5m/s 1 m off the ground
3 0
3 years ago
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