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baherus [9]
4 years ago
9

If for every action force an equal and opposite reaction force exists, how can anything ever be accelerated?

Physics
1 answer:
sweet [91]4 years ago
8 0
If there are two equal and opposite forces on the SAME THING, then the thing doesn't accelerate. You're right about that. But the action and reaction forces act on two different things. The bullet and the rifle. The ball and the bat. The airplane and the air. etc. So BOTH can accelerate.
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To obtain the same resistance force, a greater force must be exerted in a machine of lower efficiency than in a machine
Sindrei [870]

Answer: True.

Explanation:

A resistance force is also known as friction. And the efficiency of a machine is affected by friction.

A machine of lower efficiency has higher magnitude of friction than a machine of higher efficiency.

Therefore, To obtain the same resistance force, a greater force must be exerted in a machine of lower efficiency than in a machine of higher efficiency. This is true

7 0
3 years ago
Nitrogen is used to protect steel from water because nitrogen has ________.
tiny-mole [99]

Answer:

Nitrogen is used to protect steel from water because nitrogen has low reactivity.

Explanation:

Nitrogen is very low reactive element because it forms a gas when triple bond between two Nitrogen atoms. Due to low reactivity of Nitrogen the water does not react with the nitrogen and steel as well. So, for protection of steel Nitrogen is used.

4 0
3 years ago
The radius of the aorta is «10 mm and the blood flowing through it has a speed of about 300 mm/s. A capillary has a radius of ab
stealth61 [152]

Answer:

(I). The effective cross sectional area of the capillaries is 0.188 m².

(II). The approximate number of capillaries is 3.74\times10^{9}

Explanation:

Given that,

Radius of aorta = 10 mm

Speed = 300 mm/s

Radius of capillary r=4\times10^{-3}\ mm

Speed of blood v=5\times10^{-4}\ m/s

(I). We need to calculate the effective cross sectional area of the capillaries

Using continuity equation

A_{1}v_{1}=A_{2}v_{2}

Where. v₁ = speed of blood in capillarity

A₂ = area of cross section of aorta

v₂ =speed of blood in aorta

Put the value into the formula

A_{1}=A_{2}\times\dfrac{v_{2}}{v_{1}}

A_{1}=\pi\times(10\times10^{-3})^2\times\dfrac{300\times10^{-3}}{5\times10^{-4}}

A_{1}=0.188\ m^2

(II). We need to calculate the approximate number of capillaries

Using formula of area of cross section

A_{1}=N\pi r_{c}^2

N=\dfrac{A_{1}}{\pi\times r_{c}^2}

Put the value into the formula

N=\dfrac{0.188}{\pi\times(4\times10^{-6})^2}

N=3.74\times10^{9}

Hence, (I). The effective cross sectional area of the capillaries is 0.188 m².

(II). The approximate number of capillaries is 3.74\times10^{9}

3 0
3 years ago
A mass of 4kg suspended by a light string 2m long and at rest is projected horizontally with a velocity of 1.5 m/s. find the ang
Dafna11 [192]

Answer:

19.5°

Explanation:

The energy of the mass must be conserved. The energy is given by:

1) E=\frac{1}{2}mv^2+mgh

where m is the mass, v is the velocity and h is the hight of the mass.

Let the height at the lowest point of the be h=0, the energy of the mass will be:

2) E=\frac{1}{2}mv^2

The energy when the mass comes to a stop will be:

3) E=mgh

Setting equations 2 and 3 equal and solving for height h will give:

4) h=\frac{v^2}{2g}

The angle ∅ of the string with the vertical with the mass at the highest point will be given by:

5) cos\phi=\frac{l-h}{l}

where l is the lenght of the string.

Combining equations 4 and 5 and solving for ∅:

6) \phi={cos}^{-1}(\frac{l-h}{l})={cos}^{-1}(1-\frac{h}{l})={cos}^{-1}(1-\frac{v^2}{2gl})

8 0
4 years ago
Which statements accurately describe Ernest Rutherford’s experiment? Check all that apply.
Dimas [21]

Answer:

Option (1), option (4) and option (5)

Explanation:

The main observations of Ernest Rutherford's experiment are given below:

1. most of the positively charged particles pass straight, it means there is an empty space in the atom.

2. Very few positively charged particles retraces their path.

So,

The positively charged particles were deflected because like charges repel, that means they are deflected by protons.

Almost all the positively charge concentrate in a very small part which is called nucleus.

7 0
4 years ago
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