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vazorg [7]
3 years ago
14

Which of the following is not a requirement of a practical fuel? A. It must occur in abundance in nature or be easy to produce.

B. It must be made up of elements that combine easily with oxygen. C. It must contain a large amount of stored energy. D. It must be in the solid state to be used.
Physics
1 answer:
Masteriza [31]3 years ago
7 0

Answer: Option D: It must be in the solid state to be used.

A material that is used to provide energy is for work is known as fuel. For practical use, it is important that the fuel must occur in abundance or can be easily produced. It should be made of elements that can easily combine with oxygen. This is required for burning. It must produce large amount of energy. So, it must contain large amount of stored energy. It is useful only when a small quantity can produce large amount of energy. It can be in any state, solid liquid or gas.

Therefore, it is not important that it must be in the solid state to be used.

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A machine gun fires 50-g bullets at the rate of 4 bullets per second. The bullets leave the gun at a speed of 1000 m/s. What is
TEA [102]

Answer:

Average recoil force experienced by machine will be 200 N

Explanation:

We have give mass of each bullet m = 50 gram = 0.05 kg

There are 4 bullets

So mass of 4 bullets = 4×0.05 = 0.2 kg

Initial speed of the bullet u = 0 m/sec

And final speed of the bullet v = 1000 m/sec

So change in momentum P=m(v-u)=0.2\times (1000-0)=200kgm/sec

Time is given per second so t = 1 sec

We know that force is equal to rate of change of momentum

So force will be equal to F=\frac{200}{1}=200N

So average recoil force experienced by machine will be 200 N

5 0
3 years ago
Two ropes have equal length and are stretched the same way. The speed of a pulse on rope 1 is 1.4 times the speed on rope 2. Par
kondor19780726 [428]

Answer:

m1/m2 = 0.51

Explanation:

First to all, let's gather the data. We know that both rods, have the same length. Now, the expression to use here is the following:

V = √F/u

This is the equation that describes the relation between speed of a pulse and a force exerted on it.

the value of "u" is:

u = m/L

Where m is the mass of the rod, and L the length.

Now, for the rod 1:

V1 = √F/u1 (1)

rod 2:

V2 = √F/u2 (2)

Now, let's express V1 in function of V2, because we know that V1 is 1.4 times the speed of rod 2, so, V1 = 1.4V2. Replacing in the equation (1) we have:

1.4V2 = √F/u1 (3)

Replacing (2) in (3):

1.4(√F/u2) = √F/u1 (4)

Now, let's solve the equation 4:

[1.4(√F/u2)]² = F/u1

1.96(F/u2) =F/u1

1.96F = F*u2/u1

1.96 = u2/u1 (5)

Now, replacing the expression of u into (5) we have the following:

1.96 = m2/L / m1/L

1.96 = m2/m1 (6)

But we need m1/m2 so:

1.96m1 = m2

m1/m2 = 1/1.96

m1/m2 = 0.51

5 0
3 years ago
Explain the difference between general intelligence and specific intelligence.
Olegator [25]

Answer:

General intelligence refers to the existence of a broad mental capacity that influences performance on cognitive ability measures.

Specific intelligence refers to a person's aptitude in individual 'modalities' or abilities rather than the more general understanding of intelligence.

Explanation:

4 0
2 years ago
Read 2 more answers
In reaching her destination, a backpacker walks with an average velocity of 1.41 m/s, due west. This average velocity results, b
V125BC [204]
The total average velocity v=+1.41 m/s (I assume west as positive direction) is given by the total displacement, S, divided by the total time taken, t:
v= \frac{S}{t}= \frac{S_1+S_2}{t_1+t_2}
where:
-The total displacement S is the algebraic sum of the displacement in the first part of the motion (S_1=6.30 km=6300 m, due west) and of the displacement in the second part of the motion (S_2, due east).
-The total time taken t is the time taken for the first part of the motion, t_1, and the time taken for the second part of the motion, t_2. t_1 can be found by using the average velocity and the displacement of the first part:
t_1= \frac{S_1}{v_1}= \frac{6300 m}{2.49 m/s}=2530 s

t_2, instead, can be written as \frac{S_2}{v_2}, where v_2=-0.630 m/s is the average velocity of the second part of the motion (with a negative sign, since it is due east). 

Therefore, we can rewrite the initial equation as:
v=1.41 = \frac{6300+S_2}{2530- \frac{S_2}{0.630} }
And by solving it, we find the displacement in the second part of the motion (i.e. how far did the backpacker move east):
S_2=-844 m=-0.844 km

4 0
3 years ago
On a safety test course, a 1000 kg car heading north at 5 m/s collides head-on with an 800 kg car heading south at 4 m/s. At the
Luden [163]

Answer:

The speed is 3.5\frac{m}{s} and the direction is heading north.

Explanation:

In collisions the force exerted by the objects that collide is higher enough than the external forces that we can neglect that external forces, with that assumption we can use the conservation fo momentum law that states, final total momentum (pf) is equal initial total momentum (pi) if there’re not external forces or they are small enough to be neglected. Mathematically:

p_f=p_i

The total momentum is the sum of the momentum of each of the bodies we're dealing, in our case the moment of each car, then:

p_{nf}+p_{sf}=p_{ni}+p_{si}

with pn the momentum of the 1000kg car heading north and ps the 800kg car heading south. Momentum is defined as mass times velocity, then:

m_nv_{nf}+m_sv_{sf}=m_nv_{ni}+m_sv_{si} (1)

It's important to note that when we talk about momentum and velocity direction matters, so we're are going to choose a system of reference where quantities pointing north are positive and pointing south are negative. So, the initial velocity of 1000 kg car is vni=5 m/s, initial velocity of 800 kg car is vsi=-4 m/s and the final velocity of 1000 kg car is vnf=-1 m/s. Now we can solve (1) for vsf and use the values we already have:

v_{sf}=\frac{m_nv_{ni}+m_sv_{si}-m_nv_{nf}}{m_s}=\frac{(1000)(5)+(800)(-4)-(1000)(-1)}{800}

v_{sf}=3.5\frac{m}{s}

Because the sign is positive the direction is to heading north.

7 0
2 years ago
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