Physics, 24.03.2020 20:00 hooplikeapro

An electric motor draws a current of 2.50 A from a 15.0-V battery when it runs at normal speed. If the motor's armature is "jammed" so that it cannot rotate, the current suddenly rises to 10.0 A. What is the back emf of the motor when running at normal speed

Answers: 2

Show answers

Answers

Answer from: jeff6284

11.25 V

Explanation:

We know E - IR = V when E = battery emf = 15.0 V and I = current = 10.0 A when the armature is jammed. When the armature is jammed, V = 0. So

E - IR = V

15 - 10R = 0

15 = 10R

R = 15/10 = 1.5 Ω which is the resistance of the windings.

Now, the back emf V when it is running at normal speed of current I = 2.50 A,

V = E - IR = 15 - 2.5 × 1.5 = 15 - 3.75 = 11.25 V

Answer from: Quest

The low lands i believe

Answer from: Quest

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

$f\alpha \frac{dp}{dt}$

⇒ $f= k \frac{dp}{dt}$

here k is the proportionality constant whose value is 1.

$f=\frac{dp}{dt}$

$f= \frac{d[mv]}{dt}$

$f= m\frac{dv}{dt} +v\frac{dm}{dt}$

$f=ma+v\frac{dm}{dt}$ [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.

Another question on Physics

Physics, 21.06.2019 22:40

Ablock of mass m = 2.5 kg is attached to a spring with spring constant k = 710 n/m. it is initially at rest on an inclined plane that is at an angle of θ = 23° with respect to the horizontal, and the coefficient of kinetic friction between the block and the plane is μk = 0.19. in the initial position, where the spring is compressed by a distance of d = 0.16 m, the mass is at its lowest position and the spring is compressed the maximum amount. take the initial gravitational energy of the block as zero. a) what is the block's initial mechanical energy? b) if the spring pushes the block up the incline, what distance, l, in meters will the block travel before coming to rest? the spring remains attached to both the block and the fixed wall throughout its motion.

Answers: 3

Answer

Physics, 22.06.2019 06:00

Aball is thrown upward. at a height of 10 meters above the ground, the ball has a potential energy of 50 joules (with the potential energy equal to zero at ground level) and is moving upward with a kinetic energy of 50 joules. what is the maximum height h reached by the ball? consider air friction to be negligible. 1. h ≈ 10 m 2. h ≈ 50 m 3. h ≈ 30 m 4. h ≈ 40 m 5. h ≈ 20 m 003 10.0 points which of the two object shown below has the greatest kinetic energy? a m b 1 2 m v 2v 1. kinetic energies are the same. 2. a 3. b 4. unable to determine. 004 10.0 points tim, with mass 74.6 kg, climbs a gymnasium rope a distance of 3.1 m. the acceleration of gravity is 9.8 m/s 2 . how much potential energy does tim gain? answer in units of j. 005 10.0 points a car is moving at 64 miles per hour. the kinetic energy of that car is 5 × 105 j. how much energy does the same car have when it moves at 111 miles per hour? answer in units of j. 006 10.0 points an 102 kg man climbs up a 1 m high flight of stairs. the acceleration of gravity is 9.81 m/s 2 . w

Answers: 3

Answer

Physics, 22.06.2019 16:00

The solid that is formed and usually sinks to the bottom of a solution is the

Answers: 2

Answer

Physics, 22.06.2019 17:00

Explain what will happen if decomposers were apsent from a forest ecoysystem.

Answers: 1

Answer

You know the right answer?

An electric motor draws a current of 2.50 A from a 15.0-V battery when it runs at normal speed. If t...