أكاديميا - كولنز - معاجم الجيب العلمية - الفيزياء - انكليزي - فرنسي - عربي الحرف ٥_ m

Academia - Collins - Pocket Scientific Dictionaries - Physics - English - French - Arabic Letter 5_ M


moment
moment m

Determination. Torque, or rotational effect, of a force or couple about a point. The torque is the product of the force F divided by the perpendicular distance s from the point of rotation: T=Fs. The unit of torque is newton metres.

The law of moments says: When a body is in a state of balance, the sum of the moments in the clockwise direction of rotation around a point is equal to the sum of the moments in the counterclockwise direction of rotation around the same point. A clockwise torque is a torque that tends to rotate the body in this direction.

Clockwise torque about 0
Counterclockwise torque about 0


momentum
Quantity of movement

Momentum. The product of a body's mass multiplied by its speed. The unit of this vector is the kilogram-meter per second (or newton-second).

The “law of conservation of momentum” results from Newton’s laws of force. This law says that the momentum of a group of objects remains constant unless a net external force acts on it. This law applies to cases of impact, (a) below, and when the body explodes or decays (b). All trends must be measured in the same way. Therefore, U2 is negative here.

M₁U₁ + M2U2 = M1V1 + M2V2

Here, V1 is negative.

0- (M₁ + M2) = 0 = M₁V1 + M2V2

In all cases, the total momentum of the system is the same before and after the event.


motor effect
Activate my motor

The effect of a motor is the tendency to move caused by a direct current flowing in a magnetic field. Thus, the fields in some types of cathode-ray tubes deflect the stream of electrons and move the spot on the screen. If the current is in a wire, the wire itself may move.
See lefthand motor rule.

This effect lies at the basis of the work of the loudspeaker with the moving coil, the meter, and the electric motor. In all cases, the force causes a coil to move in a field.


motor, electric
Motor electric

Electrical engine. A device that converts electrical energy input into movement. In most cases, the central coil is rotatable. The structure of a simple engine is exactly like the structure of a generator. Direct current enters the coil through a slip ring, and in a simple alternating current motor, two carbon travels press two slip rings.

Since the engine is just like a generator, it actually works as a generator. Back emf appears in the moving coil, and this tends to oppose the applied voltage.
See electromagnetic induction.