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postnew [5]
3 years ago
15

If the sign of work is negative,

Physics
1 answer:
aivan3 [116]3 years ago
5 0

If the sign of work is negative, that means the force and the motion are in opposite directions.

Let's say you see something roll off of the shelf. You catch it, and you let it down slowly and gently.

Gravity exerted down-force on it and it moved down. Gravity did positive work on it.

YOU exerted UP-force on it and it moved down. YOU did negative work on it.

(Also, the falling object exerted down-force on your hand, and your hand moved down. The falling object did positive work on your hand ! Where did THAT energy come from ? It came from the potential energy that the object had while it was on the shelf. Your hand absorbed that energy on the way down, doing negative work. So the object didn't have any kinetic energy when it reached the floor, and it did NOT splinter the floor or shatter in smithereens. It had barely enough energy left to make a sound when it hit the floor.)

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ASE (National Institute for Automotive Service Excellence) certified professionals must be retested every _______ years to keep
Bess [88]
Hi,

The correct answer is C. five 

I hope I helped :)
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3 years ago
To accelerate, an object must *
Sonja [21]
Answer: Not 100% sure but I think it’s C.

Hope this helps! ^^
4 0
3 years ago
The length of a simple pendulum is 0.81 mand the mass of the particle (the "bob") at the end of the cable is0.23 kg. The pendulu
Gemiola [76]

Answer:

\displaystyle w=3.478\ rad/sec

M=0.0182\ J

v=0.398\ m/s

Explanation:

<u>Simple Pendulum</u>

It's a simple device constructed with a mass (bob) tied to the end of an inextensible rope of length L and let swing back and forth at small angles. The movement is referred to as Simple Harmonic Motion (SHM).

(a) The angular frequency of the motion is computed as

\displaystyle w=\sqrt{\frac{g}{L}}

We have the length of the pendulum is L=0.81 meters, then we have

\displaystyle w=\sqrt{\frac{9.8}{0.81}}

\displaystyle w=3.478\ rad/sec

(b) The total mechanical energy is computed as the sum of the kinetic energy K and the potential energy U. At its highest point, the kinetic energy is zero, so the mechanical energy is pure potential energy, which is computed as

U=mgh

where h is measured to the reference level (the lowest point). Please check the figure below, to see the desired height is denoted as Y. We know that

H+Y=L

And

H=L\ cos\alpha

Solving for Y

Y=L(1-cos\alpha )

Since\ \alpha=8.1^o, L=0.81\ m

Y=0.0081\ m

The potential energy is

U=mgh=0.23\ kg(9.8\ m/s^2)(0.0081\ m)

U=0.0182\ J

The mechanical energy is, then

M=K+U=0+U=U

M=0.0182\ J

(c) The maximum speed is achieved when it passes through the lowest point (the reference for h=0), so the mechanical energy becomes all kinetic energy (K). We know

\displaystyle K=\frac{mv^2}{2}

Equating to the mechanical energy of the system (M)

\displaystyle \frac{mv^2}{2}=0.0182

Solving for v

\displaystyle v=\sqrt{\frac{(2)(0.0182)}{0.23}}

v=0.398\ m/s

4 0
3 years ago
A wire along the z axis carries a current of 6.8 A in the z direction Find the magnitude and direction of the force exerted on a
Alexeev081 [22]

Answer:

Force is 14.93N along positive y axis.

Explanation:

We know that force 'F' on a current carrying conductor placed in a magnetic field of intensity B is given by

\overrightarrow{F}=\overrightarrow{Il}\times \overrightarrow{B}

where L is the length of the conductor

Applying values in the equation we have force F =

\overrightarrow{F}=6.8\times 6.1\widehat{k}\times 0.36\widehat{i}\\\\\overrightarrow{F}=41.48\widehat{k}\times 0.36\widehat{i}\\\\\therefore \overrightarrow{F}=14.93N\widehat{j}

Thus force is 14.93N along positive y axis.

3 0
3 years ago
The electron gun in a television tube accelerates electrons (mass = 9.11x10^-31 kg, charge = 1.6 x 10^-19C) from rest to 3 x10^7
stich3 [128]

Answer:

Electric field acting on the electron is  127500 N/C.

Explanation:

It is given that,

Mass of an electron, m=9.11\times 10^{-31}\ kg

Charge on electron, q=1.6\times 10^{-19}\ C

Initial speed of electron, u = 0

Final speed of electron, v=3\times 10^7\ m/s

Distance covered, s = 2 cm = 0.02 m

We need to find the electric field required. Firstly, we will find the acceleration of the electron from third equation of motion as :

a=\dfrac{v^2-u^2}{2s}

a=\dfrac{(3\times 10^7)^2-0}{2\times 0.02}

a=2.25\times 10^{16}\ m/s^2

According to Newton's law, force acting on the electron is given by :

F = ma

F=9.1\times 10^{-31}\times 2.25\times 10^{16}

F=2.04\times 10^{-14}\ N

Electric force is given by :

F = q E, E = electric field

E=\dfrac{F}{q}

E=\dfrac{2.04\times 10^{-14}}{1.6\times 10^{-19}}

E = 127500 N/C

So, the electric field is 127500 N/C. Hence, this is the required solution.

8 0
3 years ago
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