Assumption: the air resistance on this ball is negligible. Take .
a. The momentum of the ball would be approximately two seconds after it is tossed into the air.
b. The momentum of the ball would be approximately three seconds after it reaches the highest point (assuming that it didn't hit the ground.) This momentum is smaller than zero because it points downwards.
Explanation:
The momentum of an object is equal its mass times its velocity . That is: .
Assume that the air resistance on this ball is negligible. If that's the case, then the ball would accelerate downwards towards the ground at a constant . In other words, its velocity would become approximately more negative every second.
The initial velocity of the ball is . After two seconds, its velocity would have become . The momentum of the ball at that time would be around .
When the ball is at the highest point of its trajectory, the velocity of the ball would be zero. However, the ball would continue to accelerate downwards towards the ground at a constant . That's how the ball's velocity becomes negative.
After three more seconds, the velocity of the ball would be . Accordingly, the ball's momentum at that moment would be .
A _commutator_ is used in a motor to switch the direction of the magnetic field created by the current.
The rotating part of a motor that holds the electromagnets is called the __armature___.
Electric current passes through the _brushes_ and into the electromagnets in an electric motor.
A motor turns _electrical_ energy into _mechanical_ energy.
Explanation:
A commutator, which is a split ring rotary switching device, reverses the direction of the current between the external circuit and the rotor. Reversing the current reverses the magnetic field.
The armature comprises the rotating part of the motor and the electromagnets
A brush is the electrical contact for conducting current through the moving and stationary parts of an electric motor
An electric motor turns electrical energy into mechanical energy.