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Question
In a dc motor, the polarity and current are reversed by a(n) __________.Answer
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Related questions
Q:
An indication of an object's inertia is given by its ______________.
Q:
A change in motion requires a(n) ____________.
Q:
The quantity mvr is an object's
A) inertia.
B) torque.
C) linear momentum.
D) angular momentum.
Q:
The force required to move a 50.0 kg object in a 55.0 m circle at a constant speed of 2.60 m/s is
A) 0.0 N
B) 6.1 N
C) 0.12 N
D) 2.36 N
Q:
Newton's law of universal gravitation is believed to be applicable
A) to the Milky Way only.
B) on Earth and the Moon only.
C) throughout the universe.
D) to the solar system only.
E) on Earth only.
Q:
In the equation A = B/C, the A and B are said to be _______________ proportional.
A) directly
B) inversely
C) not
D) exactly
Q:
Newton's third law of motion states that the force pair acting on different objects consists of two forces that
A) are under the influence of gravity.
B) are equal and in the same direction.
C) always produce an acceleration.
D) are equal and in opposite directions.
Q:
______________ principle explains why objects float or sink in a fluid.
A) Newton's
B) Pascal's
C) Bernoulli's
D) Archimedes'
Q:
The buoyant force of an object is equal to the ______________ of the ______________ it displaces.
A) mass; fluid
B) weight; fluid
C) mass; solid
D) weight; solid
Q:
If an object of mass 8 kg has an acceleration of 5 m/s2, what is the unbalanced force acting on it?
A) 40 N
B) 1.6 N
C) 0.63 N
D) 13 N
E) cannot be determined
Q:
A spacecraft in space keeps going at the same velocity, even without firing its rockets, in accordance with the _______________ law of motion.
A) fourth
B) first
C) second
D) third
Q:
A constant net force acting on an object that is free to move will produce a constant
A) speed.
B) velocity.
C) displacement.
D) acceleration.
E) distance.
Q:
A mass is accelerated when ______________ acts upon the mass.
A) a balanced force
B) any force
C) no force
D) an unbalanced force
E) none of these
Q:
A rifle bullet shot horizontally has a vertical acceleration of ______________.
Q:
If an object has a constant velocity, then its acceleration is ______________.
Q:
The straight-line distance and direction between two points are, together, called ______________.
Q:
A projectile's vertical velocity component
A) changes most rapidly near the top of its trajectory.
B) changes at a constant rate.
C) changes most rapidly near the bottom of its trajectory.
D) does not change.
Q:
The magnitude of the acceleration of an object moving in a circle at constant speed is
A) inversely proportional to the speed squared.
B) inversely proportional to the speed.
C) inversely proportional to the radius of the circle squared.
D) inversely proportional to the radius of the circle.
Q:
The direction of the acceleration of an object moving in a circle at constant speed is
A) changing, but pointing in a predictable direction.
B) constant and pointing in only one direction.
C) constant and pointing in two directions.
D) none of these
Q:
An object travels in a circle of radius 10.0 m with a constant speed of 3.0 m/s. What is the direction of its acceleration?
A) Toward the center of the circle
B) Normal to the plane of the circle
C) Insufficient data given for determination
D) Tangential to the circle
E) None of these
Q:
In the equation ac= v2/rfor centripetal acceleration, the v stands for
A) volume.
B) very.
C) speed.
D) velociraptor.
Q:
A freely falling object has a constant acceleration of 9.8 m/s2. This means that
A) the object's displacement changes by 9.8 m every second squared.
B) the object's speed increases by 9.8 m/s each second.
C) the object's acceleration increases by 9.8 m/s2each second.
D) the object travels 9.8 m each second.
Q:
An object with a mass of 8 kg is dropped and takes 5 s to hit the ground. Then another object with a mass of 16 kg is dropped from the same point. How long does it take to hit the ground?A) 5 sB) 10 sC) 3 sD) 25 sE) 125 s
Q:
A freely falling object
A) has a uniformly increasing velocity.
B) is unaffected by gravity.
C) has a uniformly increasing acceleration.
D) has a uniformly increasing displacement.
Q:
An object that is moving in a linear path with an acceleration at a right angle to the motion has a(n) ______________ velocity.
A) changing
B) increasing
C) decreasing
D) constant
Q:
The distance traveled by an automobile moving at a constant velocity is
A) directly proportional to the time.
B) directly proportional to the time squared.
C) inversely proportional to the time squared.
D) inversely proportional to the time.
E) none of these
Q:
An acceleration may result from
A) a change in speed.
B) a change in direction.
C) a change in both speed and direction.
D) all of these
Q:
If an object moves with constant velocity,
A) its speed is constant.
B) its direction is constant.
C) its average speed is constant.
D) its distance traveled per unit time is constant.
E) all of these
Q:
An ant on a picnic table travels 30 cm eastward, then 15 cm northward, then 20 cm westward, and finally 15 cm southward. What is the magnitude of its net displacement?
Q:
A car travels at a constant speed of 100.0 km/h around a circular track with a diameter of 1.00 km. What is the magnitude of the car's centripetal acceleration, and what supplies this?