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alisha [4.7K]
3 years ago
9

Please help with 4 and 5, thank you :)

Physics
1 answer:
allochka39001 [22]3 years ago
6 0

Answer: #4

Sally is faster.

Explanation:

If you multiply Sallies it is going to be less than Jessica's.

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Which of the following is not an example of a chemical reaction? Rust, Photosynthesis, Melting Ice, Heat from Fire?
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Rust, photosynthesis, and heat from fire are all chemical reactions <span>because </span>new substances are formed and the chemical formula is changed. By doing this, bonds are broken and formed in the making of the new substance. Melting ice is physical change the molecules are still water molecules, it just changed physical form. 
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You have 4.9 g of an unknown substance. To identify the substance, you decide to measure its specific heat and find that it requ
kifflom [539]

The unknown substance can be lithium, which has a specific heat capacity of approximately 3.5 J/gK.

Explanation:

When heat energy is supplied to a certain substance, the temperature of the substance increases according to the equation:

Q=mC_s \Delta T

where

Q is the amount of energy supplied

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In this problem, we have

m = 4.9 g is the mass

Q = 668.85 J is the specific heat capacity

\Delta T = 39 K is the change in temperature

Solving for C_s, we find the specific heat capacity of the substance:

C_s = \frac{Q}{m\Delta T}=\frac{668.85}{(4.9)(39)}=3.5 J/gK

Looking at tables of specific heat capacity, we can see that the unknown substance can be lithium, which has a specific heat capacity of approximately 3.5 J/gK.

Learn more about specific heat capacity:

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3 years ago
A tennis player smashes a ball of mass m horizontally at a vertical wall. The ball rebounds at the same speed v with which it st
Morgarella [4.7K]

Answer:

<em> B.0</em>

Explanation:

Change in momentum: This is defined as the product of mass and change in velocity of a body. or it can be defined as the product of force and time of a body. The fundamental unit of change in momentum is kg.m/s

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Let: M = m kg and V = U = v m/s

Substituting these values into equation 1

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Change in momentum = m(0)

Change in momentum = 0 kg.m/s

<em>Therefore the momentum of the ball has not changed.</em>

<em>The right option is B.0</em>

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strain energy is 0. 5x force x (compression) X (compression)
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