Science Flashcards
You are standing on a scale in an elevator. You notice that your weight is decreasing.
What can you conclude? The elevator is_ .
a. Accelerating upward
b. Moving at constant acceleration upward
c. Accelerating downward
d. Moving at constant acceleration downward
D
If the force of gravity on balloon is 3,000N, and the lift force provided by the atmosphere is 2,900N, in which direction is the net force acting?
a. Upward
b. towards the east
c. Downward
d. there is no net force
C
If a horse pulls on a calesa at rest, the calesa pulls back equally as much on the horse. Will the calesa be set into motion?
a. No, because the forces cancel each other.
b. Yes, because there is a net force acting on the calesa.
c. Yes, because there is a time delay between action and reaction.
d. Yes, because the horse’s pull on the calesa is larger than the calesa’s pull on the horse.
B
Which of the following statements is not one of Newton’s Laws on motion?
a. In the absence of an unbalanced force, an object moves at constant velocity
b. For any force there is always an equal but opposite reaction force.
c. The force and the acceleration of a body are towards the same direction.
d. What goes up must come down.
D
Two cars are following a 35 ton tractor-trailer truck traveling down the highway at a high rate of speed. One of the following vehicles is significantly heavier than the other. Wind coming off the back of the truck shakes them both. One of them does not sway as much as the other. Which one does not sway as much as the other?
a. The lighter car will sway more than the heavier car.
b. The heavier car will sway more than the lighter car.
c. A only
d. A and B
C
When an object is placed in front of a plane mirror the image is:
a. Upright, magnified and real
b. Upright, the same size and virtual
c. Inverted, demagnified and real
d. Inverted, magnified and virtual
e. Upright, magnified and virtual
B
A narrow beam of light is incident on the surface of a plane mirror. The initial angle between the incident ray and reflected ray is 2α. If the mirror is turned around point A by the angle Θ what is the change of the angle between two rays?
(A) Θ (B) 2Θ (C) 4Θ (D) Θ/2 (E) Θ/4
B
A candle is placed in front of a concave mirror. The image produced by the mirror is:
a. Real, inverted and magnified
b. Real, inverted and demagnified
c.Virtual, upright and magnified
d. Virtual, upright and demagnified
e. Real, upright and magnified
A
A very narrow light ray AB strikes the surface of a concave mirror as shown on the diagram. Which of the following diagrams represents the reflected ray?
B
Which of the following are the postulates of special relativity?
I. The color of light is the same for all frames of reference.
II.The speed of light is the same for all frames of reference.
III. The relative speed of objects is the same for all observes in moving frames of reference.
A. I and II
B. I and III
C. II and III
D. II and IV
D
One of two identical twins is an astronaut, while the other is areal estate broker. The astronaut embarks on high speed space travel and is gone for several years. Upon the astronaut’s return, the two twins reunite and observed their physical appearances. The observation will be that .
A. Both have aged the same
B. The astronaut has aged less
C. The astronaut more
D. The real estate broker has aged less
B
The following physical quantities are classified as the fundamental quantities of measure: time, length, and mass. The mass of the body is believed to be constant wherever it is taken and we consider it also the same whether the body is in motion or at rest. However, Einstein considers the mass of a moving body not constant. Why is this so can be understood by the law of acceleration. Recall that acceleration depends not only on force but also on the mass of the object as well. Einstein believed that when work is done on the object to increase its velocity, its mass increases as well. So, the force produces less and less acceleration as velocity increases. The relationship between mass and velocity is given in the following equation:
m = the mass of the body when it is in motion, Mo = mass of the body when it is at rest
What is the mass of the electron traveling at half the speed of light? (Mass of an electron at rest is 9.11 x 10-31 kg.)
A. 1.05 𝑥 10 -30 𝑘g
B. 2.05 𝑥 10 -30 𝑘g
C. 1.05 𝑥 10 -29 𝑘g
D. 2.05 𝑥 10 -29 𝑘g
A
In the special theory of relativity, it is important to know the velocity of an object relative
to an observer. It plays a very important role in attaining the effects of time dilation, length contraction, relativistic momentum, and energy-mass transformation. If we are to determine the velocity of an object relative to that of an observer, oftentimes we have to add two or more velocities together in an equation. According to the special theory of
elativity, the velocities are related according to the velocity-addition equation:
u = the velocity of the object as measured by an observer on Earth,
u’ = the velocity of the object as measured by an observer in the moving frame which itself is moving at a velocity, v, relative to Earth.
A car is approaching an observer on Earth with a velocity v = 0.85c. A person in the car throws a ball towards the observer at a velocity of u’ = 0.60c relative to the car. At what velocity does the observer on Earth see the ball approaching?
A. 0.196𝑐 B. 0.916𝑐 C. 0.96𝑐 D. 0.916𝑐
C
Microwaves were invented during World War II when radar technology was being
developed. In the last 40 years, the microwave oven has become a ubiquitous appliance. Microwave technology enables us to thaw and cook food much more rapidly than conventional appliances do. The cooking action in a microwave oven results from the interaction between the electric the field component of the radiation with the polar molecules—mostly water—in food. All molecules rotate at room temperature. If the frequency of the radiation and that of the molecular rotation are equal, energy can be transferred from the microwave to the polar molecule. As a result, the molecule will rotate faster. This is what happens in a gas. In the condensed state (for example, in food), a molecule cannot execute the free rotation. Nevertheless, it still experiences a torque (a force that causes rotation) that tends to align its dipole moment with the oscillating field of the microwave. Consequently, there is friction between the molecules, which appears as heat in the food. (Source).
Which of the following statements best describe why microwaves heat food so quickly?
A. The radiation is absorbed by nonpolar molecules that created friction and will generate heat in food.
B. The radiation is absorbed by polar molecules and can, therefore, reach different parts of food at the same time.
C.The polar molecules in foods when exposed to radiation will heat and cooks the food.
D. The nonpolar molecules in foods when exposed to radiation will heat and cooks the food.
B
Read the following information and answer the question below.
Which of the following statements is correct about food containers that are utilized and safe for microwaves?
A. They do not contain polar molecules and are therefore not affected by microwaves.
B. They contain polar molecules and are therefore affected by microwaves.
C. They do not contain nonpolar molecules and are therefore not affected by microwaves.
D. They contain nonpolar molecules and are therefore affected by microwaves.
A