Physics Problems for 9 – 30 – 16

Problem 1

A distance of 1.0 × 10−2 meter separates successive crests of a periodic wave produced in a shallow tank of water. If a crest passes a point in the tank every 4.0 × 10−1 second, what is the speed of this wave?
(1) 2.5 × 10−4 m/s
(2) 4.0 × 10−3 m/s
(3) 2.5 × 10−2 m/s
(4) 4.0 × 10−1 m/s

Una distancia de 1.0×102 metro separa crestas sucesivas de una onda periódica producida en un tanque de vacío de agua. Si una cresta pasa un punto en el tanque cada 4.0×101 segundo, ¿cuál es la rapidez de esta onda?
(1) 2.5 x 104 m/s
(2) 4.0 x 103 m/s
(3) 2.5 x 102 m/s
(4) 4.0 x 101 m/s

Discussion and Solution:
Velocity is calculated by dividing distance travelled by the time of travel:

v = d/t.

Substituting in what we know, we get:

v = (1.0 x 10-2 m)/(4.0 x 10-1 s) = 2.5 x 10-2 m/s.

Choice (3).

Problem 2

The electronvolt is a unit of
(1) energy
(2) charge
(3) electric field strength
(4) electric potential difference

El electronvoltio es una unidad de
(1) energía
(2) carga
(3) intensidad de campo eléctrico
(4) diferencia potencial eléctrica

Discussion and Solution:
Straight definition/memorization.
Choice (1).

Problem 3

Which particle would produce a magnetic field?
(1) a neutral particle moving in a straight line
(2) a neutral particle moving in a circle
(3) a stationary charged particle
(4) a moving charged particle

¿Cuál partícula produciría un campo magnético?
(1) una partícula neutral moviéndose en una línea recta
(2) una partícula neutral moviéndose en un círculo
(3) una partícula cargada estacionaria
(4) una partícula cargada en movimiento

Discussion and Solution:
When charged particles move (e.g., electrons in a wire), a magnetic field is produced. In the same manner, when a magnetic field is moved, an electric current is produced.
Choice (4).

Problem 4

A physics student takes her pulse and determines that her heart beats periodically 60 times in 60 seconds. The period of her heartbeat is
(1) 1 Hz
(2) 60 Hz
(3) 1 s
(4) 60 s

Una estudiante de física toma su pulso y determina que su corazón late periódicamente 60 veces en 60 segundos. El período de los latidos del corazón es
(1) 1 Hz
(2) 60 Hz
(3) 1 s
(4) 60 s

Discussion and Solution:
Period is defined as the time for one event to occur. To do this, we divide the total time by the total number of occurrences:

(60 s)/(60) = 1 s.

Choice (3).

Problem 5

Moving 4.0 coulombs of charge through a circuit requires 48 joules of electric energy. What is the potential difference across this circuit?
(1) 190 V
(2) 48 V
(3) 12 V
(4) 4.0 V

Mover 4.0 coulombs de carga a través de un circuito requiere 48 joules de energía eléctrica. ¿Cuál es la diferencia potencial a través de este circuito?
(1) 190 V
(2) 48 V
(3) 12 V
(4) 4.0 V

Discussion and Solution:
Use the formula, V = W/q, where V = potential difference, W = work, and q = charge.
Substituting in what we know, we get:

V = W/q = (48 J)/ (4.0 C) = 12 V

Choice (3).

 

 

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