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3 years ago

Which of the following has zero acceleration?

2 answers:

5 0

'Acceleration' means any change in speed or direction
of motion.

so
C). No acceleration. Straight, at constant speed.
No change of speed or direction.

anyanavicka [17]3 years ago

3 0

Answer:

C. A person running 100 m straight across a field at a constant speed.

Explanation:

Acceleration is defined as the change in the velocity per unit time. Velocity have both direction and magnitude (speed) . So, acceleration involves both change in direction and speed.

A). The satellite is in a curved orbit, so direction of satellite is constantly changing. Hence, not the answer.

B). The car is following a curve, so its direction is changing. Hence, not the answer.

C). The person is running straight at constant speed which means no change of speed or direction. Hence, it is the answer.

D). The person is on curved track, so his/her direction is changing. Hence, not the answer.

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Consider the reaction:

murzikaleks [220]

Answer: The formation of given amount of oxygen gas results in the absorption of 713 kJ of heat.

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of oxygen gas = 83 g

Molar mass of oxygen gas = 32 g/mol

Putting values in above equation, we get:

$\text{Moles of oxygen gas}=\frac{83g}{32g/mol}=2.594mol$

For the given chemical equation:

$2Fe_2O_3\rightarrow 4Fe+3O_2;\Delta H^o_{rxn}=+824.2kJ$

Sign convention of heat:

When heat is absorbed, the sign of heat is taken to be positive and when heat is released, the sign of heat is taken to be negative.

By Stoichiometry of the reaction:

When 3 moles of oxygen gas is formed, the amount of heat absorbed is 824.2 kJ

So, when 2.594 moles of oxygen gas is formed, the amount of heat absorbed will be = $\frac{824.2kJ}{3mol}\times 2.59mol=713kJ$

Hence, the formation of given amount of oxygen gas results in the absorption of 713 kJ of heat.

7 0

4 years ago

Which of the following is true regarding the law of conservation of mass?

nexus9112 [7]

A is correct................

8 0

3 years ago

The half-life of sr-90 is 28 years. after 56 years of decay only 0. 40 g of a sample remains. what was the mass of the original

Svetradugi [14.3K]

Half-life is the time taken for the concentration of the substance to reduce by 50%. The original sample of strontium had a mass of 1.6 gms. Thus, option d is correct.

The half-life of any radioactive substance is the time period at which the concentration will get reduced to half the initial amount. The initial mass of Sr-90 is calculated as,

$N(t) = N_{0} (\dfrac{1}{2})^{ \frac{t }{t 1/2}}$

Given,

Quantity of the remaining substance N (t) = 0.40 gm

Initial radioactive substance quantity $N_{0}$ =?

Time duration (t) = 56 years

Half-life = 28 years

Substituting values above:

$\begin{aligned} 0.40 &= N_{0} (\dfrac{1}{2}) ^{{\frac{56}{28}}\\\\0.40 &= N_{0} (\dfrac{1}{2})^{2}\end{aligned}$

= 1.6 gm

Therefore, option d. the initial mass of Sr is 1.6 gm.

Learn more about half-life here:

brainly.com/question/16145921

#SPJ4

7 0

2 years ago

A chemist has one solu6on that is 40% sulfuric acid and one that is 10% sulfuric acid. How much of each should she use to make 2

kipiarov [429]

Answer:

12 L of 40% sulfuric acid solution and 8 L of 10% sulfuric acid solution are needed to make 20 L of sulfuric acid solution.

Explanation:

For first solution of sulfuric acid :

C₁ = 40% , V₁ = ?

For second solution of sulfuric acid :

C₂ = 10% , V₂ = ?

For the resultant solution of sulfuric acid:

C₃ = 28% , V₃ = 20L

Also,

V₁ + V₂ = V₃ = 20L ......................................(1)

Using

C₁V₁ + C₂V₂ = C₃V₃

40×V₁ + 10×V₂ = 28×20

So,

40V₁ + 10V₂ = 560........................................(2)

Solving 1 and 2 as:

V₂ = 20 - V₁

Applying in 2

40V₁ + 10(20 - V₁) = 560

40V₁ + 200 - 10V₁ = 560

30V₁ = 360

V₁ = 12 L

So,

V₂ = 20 - V₁ = 8L

12 L of 40% sulfuric acid solution and 8 L of 10% sulfuric acid solution are needed to make 20 L of sulfuric acid solution.

4 0

4 years ago

What can we learn about past climate changes from ice cores?

Mice21 [21]

Fossil fuels about into Earth ice age time

6 0

3 years ago