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Harrizon [31]
4 years ago
12

A person throws a ball straight up in the air. The ball rises to a maximum height and then falls back down so that the person ca

tches it. Consider the ball while it is in the air. Which of the following statements are true? Just after the ball leaves the person's hand the direction of the acceleration is up. The acceleration is zero when the ball reaches its maximum height. The acceleration is about 9.8 m/s2 (down) when the ball is falling.
Physics
1 answer:
Lana71 [14]4 years ago
5 0

Answer:

The acceleration is about 9.8 m/s2 (down) when the ball is falling.

Explanation:

The ball at maximum height has velocity zero

t = Time taken

u = Initial velocity

v = Final velocity

s = Displacement

a = Acceleration due to gravity = 9.8 m/s² (positive downward and negative upward)

v=u+at\\\Rightarrow 0=u-9.8\times t\\\Rightarrow u=9.8t

The accleration 9.8 m/s² will always be acting on the body in opposite direction when the body is going up and in the same direction when the body is going down. The acceleration on the body will never be zero

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What is the function of the commutator in a DC motor? A. to spin the magnet B. to change direct current into alternating current
sergejj [24]

Answer

Correct Answer is B(to change direct current into alternating current)

Explanation

commutation

The main aim of commutation is to maintain the torque acting on armature of DC motros in the same direction.

commutator  a switch which is used to convert the direction of flow of electric current  it is connected to the armature of DC motor.

In DC motors, voltage across the armature is alternating in nature. The direction of  this current is reverses by Commutator when armature of DC motors  passes through magnetic neutral axis to maintain the unidirectional. Hence, commutator is used to change direct current into alternating current.


6 0
3 years ago
Which is longer, 10 cm or .01 m?
motikmotik

Answer:

They´re the same.

Explanation:

Someone deleted my answer. And my brainly is gone..

Have a good night ma´am/sir.

Be safe!

6 0
3 years ago
A piston above a liquid in a closed container has an area of 1m2. The piston carries a load of 350 kg. What will be the external
ddd [48]
The weight of the load is (mass) x (gravity)

                               = (350 kg) x (9.8 m/s²)

                               =        3,430 newtons .

The force on the surface of the liquid is the weight of the piston and its load.

The pressure on the surface of the liquid is  (force) / (area) 

                                                             =  (3,430 newtons) / (1 m²)

                                                             =  3,430 pascals

                                                             =      3.43 kPa

This doesn't include anything for the weight of the piston without its load,
but it's certainly the closest of the choices.
7 0
4 years ago
Read 2 more answers
Rotor windings in wound rotor motors are connected to ? on the shaft of the motor. Brushes allow those windings to be connected
Mashutka [201]

Answer:

Slip Rings

Explanation:

The wound rotor motor has a three-phase winding with each one connected to seperate slip rings. These slip rings contain brushes which form a secondary circuit where resistance can be inserted and this will allow for the rotor current to run more in phase with the stator current which will result in increased torque that is created

6 0
4 years ago
What is the internal energy of 3.00 mol of N2 gas at 25 degrees C? To solve this problem, use the equation: U electronic gas = 5
allochka39001 [22]

<u>Given data</u>

Determine Internal energy of gas N₂,  (U) = ?

Temperature (T) = 25° C

                          = 25+273 = 298 K,

Gas constant (R) = 8.31 J/ mol-K ,

Number of moles (n) = 3 moles,

<u>Internal energy of N₂ </u>

Internal energy is a property of thermodynamics, the concept of internal energy can be understand by ideal gas. For example N₂, the observations for oxygen and nitrogen at atmospheric temperatures,  f=5,  (where f is translational  degrees of freedom).

       So per kilogram of gas,

          The internal energy (U) = 5/2 .n.R.T

                                                  = (5/2) × 3 × 8.31 ×298

                                                  = 18572.85 J

<em>The internal energy of the N₂ is 18,572.85 J and it is approximately equal to 18,600 J given in the option B.</em>

 



8 0
3 years ago
Read 2 more answers
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