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Advocard [28]
3 years ago
12

After performing a long equation using the conservation of mechanical energy you get a final answer that is negative. What does

this mean?
A. Because energy is scalar it means that the energy is less than 0.

B. Because energy is scalar it means that the energy was transferred somewhere else.

C. Because energy is a vector it means that the energy was destroyed in the opposite direction.

D. Because energy is scalar it means that the energy was destroyed.
Physics
1 answer:
AfilCa [17]3 years ago
4 0

Answer:

The correct option is D.

Explanation:

The energy is the capacity to do work.

There are several types of energies.

1. kinetic energy : it is due to the motion of the body.

2. Potential energy : It is due to the position or the configuration of the body.

3. Mechanical energy: The sum of the kinetic energy and the potential energy is called mechanical energy.

The energy is a scalar quantity.

According to the law of conservation of energy, the energy can not be created and cannot be destroyed, it can transformed from one form to another.

When we get the mechanical energy negative, it means the energy was destroyed in some other forms of energy.  

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Two horizontal rods are each held up by vertical strings tied to their ends. Rod 1 has length L and mass M; rod 2 has length 2L
antiseptic1488 [7]

Answer:

Rod 1 has greater initial angular acceleration; The initial angular acceleration for rod 1 is greater than for rod 2.

Explanation:

For the rod 1 the angular acceleration is

\tau_1 = I_1\alpha _1 \\\\\alpha_1 = \dfrac{\tau_1}{I_1}

Similarly, for rod 2

\alpha_2 = \dfrac{\tau_2}{I_2}.

Now, the moment of inertia for rod 1 is

I_1 = \dfrac{1}{3}ML^2,

and the torque acting on it is (about the center of mass)

\tau_1 = Mg\dfrac{L}{2};

therefore, the angular acceleration of rod 1 is  

\alpha_1 = \dfrac{Mg\dfrac{L}{2}}{\dfrac{1}{3}ML^2},

\boxed{\alpha_1 = \dfrac{3g}{2L} }

Now, for rod 2 the moment of inertia is

I_2 = \dfrac{1}{3}(2M)(2L)^2

I_2 = \dfrac{8}{3} ML^2,

and the torque acting is (about the center of mass)

\tau _2 = (2M)g \dfrac{(2L)}{2}

\tau _2 = 2MgL;

therefore, the angular acceleration \alpha_2 is

\alpha_2 = \dfrac{2MgL;}{\dfrac{8}{3} ML^2,}.

\boxed{\alpha_2 = \dfrac{3g}{4L}}

We see here that

\dfrac{3g}{2L} > \dfrac{3g}{4L}

therefore

\boxed{\alpha_1 > \alpha_2.}

In other words , the initial angular acceleration for rod 1 is greater than for rod 2.

7 0
3 years ago
Why is knowing the direction of the force important?
vodomira [7]
Knowing the direction of a force is important because it helps someone know the motion of the object. if you use a free body diagram, then it becomes easy to see all the forces being applied to an object. if there is more force going one way, the object is accelerating in that direction. if all the forces cancel each other out, then the object is at a constant speed or is at rest.
4 0
3 years ago
PLEASE HELP AS SOON AS POSSIBLE!!!
Brums [2.3K]

Answer:

h = 81.63 m

Explanation:

Given that,

The speed of the car, v = 40 m/s

We need to find the height when the car comes to rest. We can use the conservation of energy to find it i.e.

mgh=\dfrac{1}{2}mv^2\\\\h=\dfrac{v^2}{2g}\\\\h=\dfrac{(40)^2}{2\times 9.8}\\\\h=81.63\ m

So, it will reach to a height of 81.63 m and comes to rest.

7 0
3 years ago
Since most people who are electrocuted don’t blow up, what kills them?
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8 0
4 years ago
At time t=0 a 2150 kg rocket in outer space fires an engine that exerts an increasing force on it in the +x−direction. This forc
amm1812

Explanation:

Given that,

Mass of the rocket, m = 2150 kg

At time t=0 a rocket in outer space fires an engine that exerts an increasing force on it in the +x−direction. The force is given by equation :

F=At^2

Here F = 888.93 N when t = 1.25 s

(c) We can find the value of A first as :

F=At^2\\\\A=\dfrac{F}{t^2}\\\\A=\dfrac{888.93}{(1.25)^2}\\\\A=568.91\ N/s^2

The value of A is 568.91\ N/s^2.

(a) Let J is the impulse does the engine exert on the rocket during the 4.0 s interval starting 2.00 s after the engine is fired. It is given in terms of force as :

J=\int\limits {F{\cdot} dt}

Limits will be from 2 s to 2+ 4 = 6 s

It implies :

J=\int\limits^6_2 {At^2{\cdot} dt}\\\\J=A\int\limits^6_2 {t^2{\cdot} dt}\\\\J=A\dfrac{t^3}{3}|_2^6\\\\J=568.91\times \dfrac{1}{3}\times (6^3-2^3)\\\\J=39444.42\ Ns

(b) Impulse is also equal to the change in momentum as :

J=m\Delta v\\\\\Delta v=\dfrac{J}{m}\\\\\Delta v=\dfrac{39444.42}{2150}\\\\\Delta v=18.34\ m/s

Hence, this is the required solution.

5 0
3 years ago
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