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3 years ago

True or False: Chemical energy stored in food cannot be transformed into mechanical energy

Physics

2 answers:

Novosadov [1.4K]3 years ago

7 0

The answer to this question is false.

nordsb [41]3 years ago

3 0

It's false. it can be transform

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What happens to kinetic energy of a snowball as it rolls across the lawn and gains mass

Naya [18.7K]

If an object whose mass is growing keeps the same, unchanged
kinetic energy, then its motion must slow down, because

Kinetic Energy = (1/2) (mass) (speed)² .

3 0

4 years ago

Read 2 more answers

A 4.2-g bullet is fired at a speed of 370 m/s into a stationary lead block, which moves a distance of 1.2 m before coming to res

Natali5045456 [20]

Answer:

(a) F = 239.575 N (b) t = 0.00649s or 6.49 ms

Explanation:

(a) By law of energy conservation, the bullet kinetic energy will be transferred to work done on stopping it from moving.

Formula for Kinetic Energy $E_k = \frac{mv^2}{2}$ where m is bullet mass, v is the velocity

Formula for work $W = FS$ where F is the average force and S is the distance travelled.

$E_k = W$

$\frac{mv^2}{2} = FS$

$F = \frac{mv^2}{2S}$

Substitute m = 4.2 g = 0.0042 kg, v = 370 m/s and S = 1.2 (m)

$F = \frac{0.0042*370^2}{2*1.2} = 239.575 N$

(b) If the force is constant, since the mass is constant and F = ma according to Newton's 2nd law, the acceleration on bullet is also constant

$a = \frac{F}{m} = \frac{239.575}{0.0042} = 57041.67 (m/s^2)$

We also have $v(t) = v_0 + at$

At the time the bullet is coming to rest, $v(t) = 0, a = -57041.67 m/s^2$

Therefore, $0 = 370 - 57041.67t$

$t = \frac{370}{57041.67} = 0.00649 s = 6.49 ms$

3 0

4 years ago

Radon-222 ( 222/86 Rn) is a radioactive gas with a half-life of 3.82 days. A gas sample contains 4.1 e 8 radon atoms initially.

kow [346]

Answer :

(a) The number of radon atoms will remain after 12 days is, $4.67\times 10^7$

(b) The number of radon nuclei have decayed by this time will be, $3.6\times 10^8$

Explanation :

Half-life = 3.82 days

First we have to calculate the rate constant, we use the formula :

$k=\frac{0.693}{t_{1/2}}$

$k=\frac{0.693}{3.82\text{ days}}$

$k=1.81\times 10^{-1}\text{ days}^{-1}$

Now we have to calculate the number of radon atoms will remain after 12 days.

Expression for rate law for first order kinetics is given by:

$t=\frac{2.303}{k}\log\frac{a}{a-x}$

where,

k = rate constant = $1.81\times 10^{-1}\text{ days}^{-1}$

t = time passed by the sample = 12 days

a = initially number of radon atoms = $4.1\times 10^8$

a - x = number of radon atoms left = ?

Now put all the given values in above equation, we get

$12=\frac{2.303}{1.81\times 10^{-1}}\log\frac{4.1\times 10^8}{a-x}$

$a-x=4.67\times 10^7$

Thus, the number of radon atoms will remain after 12 days is, $4.67\times 10^7$

Now we have to calculate the number of radon nuclei will have decayed by this time.

The number of radon nuclei have decayed = Initial number of radon atoms - Number of radon atoms left

The number of radon nuclei have decayed = $(4.1\times 10^8)-(4.67\times 10^7)$

The number of radon nuclei have decayed = $3.6\times 10^8$

Thus, the number of radon nuclei have decayed by this time will be, $3.6\times 10^8$

5 0

3 years ago

I AM TIMED !! 30 POINTS Which is the smallest possible particle of an element?

zimovet [89]

Answer:

atoms

Explanation:

they are the smallest

4 0

3 years ago

Read 2 more answers

The internal energy of nmoles of an ideal gas depends on a. one state variable T.

VMariaS [17]

Answer:

Correct option a. one state variable T.

Explanation:

In the case of an ideal gas it is shown that internal energy depends exclusively on temperature, since in an ideal gas any interaction between the molecules or atoms that constitute it is neglected, so that internal energy is only kinetic energy, which depends Only of the temperature. This fact is known as Joule's law.

The internal energy variation of an ideal gas (monoatomic or diatomic) between two states A and B is calculated by the expression:

ΔUAB = n × Cv × (TB - TA)

Where n is the number of moles and Cv the molar heat capacity at constant volume. Temperatures must be expressed in Kelvin.

An ideal gas will suffer the same variation in internal energy (ΔUAB) as long as its initial temperature is TA and its final temperature TB, according to Joule's Law, whatever the type of process performed.

3 0

3 years ago