ACT Science : Physics
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Example Question #21 : Physics
Black-body radiation is the energy that is released as light from any object with a non-zero temperature (0 Kelvin, or about –273.15 degrees Celcius). An everyday example of black-body radiation is an electric stovetop. When an electric stove is at its highest setting, energy is pumped into the stovetop, and some of the energy will be released as light, causing it to glow orange. This is black-body radiation at the wavelength of light that corresponds with the color orange.
The visible spectrum of light wavelengths is from about 400 nanometers (high energy) to about 750 nanometers (low energy). The wavelength of light is correlated with the energy of that light, while the intensity refers to the amount of light. For example, a stovetop with very bright orange color does not have different energy per photon of light than a stovetop with a dim orange, as long as they are the same shade. Rather, the brighter stovetop just emits more photons.
Based on the information in the passage, why don't we see regular objects like tables and chairs radiating light like a stovetop?
Objects at room temperature exhibit black-body radiation at wavelengths greater than 750 nanometers.
Objects at room temperature exhibit black-body radiation at wavelengths less than 400 nanometers.
Objects at room temperature need to be heated to have black-body radiation.
Objects at room temperature need to be cooled to have black-body radiation.
Objects at room temperature do not exhibit black-body radiation.
Objects at room temperature exhibit black-body radiation at wavelengths greater than 750 nanometers.
The passage states that black body radiation occurs with any object at a non-zero temperature. This means that objects at room temperature also exhibit black-body radiation. So, why don't we see it? The answer lies in what the passage says about wavelength and energy. As the passage states, a stove may begin to glow when provided with energy. Conversely, an object at room temperature has much less energy than a heated stove and therefore still displays black-body radiation except at a frequency that corresponds to lower energy. The passage tells us that higher wavelengths are associated with lower energy, leading us to conclude that objects at room temperature are emitting light, but at wavelengths above the visible spectrum, or above 750 nanometers.
Example Question #22 : Physics
Black-body radiation is the energy that is released as light from any object with a non-zero temperature (0 Kelvin, or about –273.15 degrees Celcius). An everyday example of black-body radiation is an electric stovetop. When an electric stove is at its highest setting, energy is pumped into the stovetop, and some of the energy will be released as light, causing it to glow orange. This is black-body radiation at the wavelength of light that corresponds with the color orange.
The visible spectrum of light wavelengths is from about 400 nanometers (high energy) to about 750 nanometers (low energy). The wavelength of light is correlated with the energy of that light, while the intensity refers to the amount of light. For example, a stovetop with very bright orange color does not have different energy per photon of light than a stovetop with a dim orange, as long as they are the same shade. Rather, the brighter stovetop just emits more photons.
A scientist decides to conduct an experiment to see how the temperature of an object affects the total energy released in its black body radiation. The scientist conducts the experiment at very low temperatures and measures the energy released by the object in units of a hundred-millionth of a joule 
Based on the data collected, how can we describe the relationship between the temperature of an object, and the total energy released as black body radiation?
Positive, non-linear relationship
Positive, linear relationship
Negative, non-linear relationship
There is no discernable relationship
Negative, linear relationship
Positive, non-linear relationship
The correct answer is that the relationship is positive and non-linear. As we see from trial 2 to 3, doubling the temperature more than doubles the energy released. This tells us that it is a positive relationship but it is most certainly non-linear.
Example Question #23 : Physics
Black-body radiation is the energy that is released as light from any object with a non-zero temperature (0 Kelvin, or about –273.15 degrees Celcius). An everyday example of black-body radiation is an electric stovetop. When an electric stove is at its highest setting, energy is pumped into the stovetop, and some of the energy will be released as light, causing it to glow orange. This is black-body radiation at the wavelength of light that corresponds with the color orange.
The visible spectrum of light wavelengths is from about 400 nanometers (high energy) to about 750 nanometers (low energy). The wavelength of light is correlated with the energy of that light, while the intensity refers to the amount of light. For example, a stovetop with very bright orange color does not have different energy per photon of light than a stovetop with a dim orange, as long as they are the same shade. Rather, the brighter stovetop just emits more photons.
The above diagram displays the amount of light emitted as black-body radiation at different wavelengths by an object. If the color violet corresponds to wavelengths around 400 nanometers, and the color red corresponds to wavelengths of around 600 nanometers; how can we describe the black-body radiation of the above object?
The black-body radiation is not visible.
The black-body radiation has a shade close to violet.
More information is necessary.
The black-body radiation has a shade exactly between violet and red.
The black-body radiation has a shade close to red.
The black-body radiation has a shade close to violet.
The correct answer is that it would emit light at a shade close to violet. The literal peak in the diagram shows where the most energy is being directed in terms of wavelength; therefore, the object is likely to appear a violet shade as opposed to a red shade.
Example Question #21 : Physics
Engineers are evaluating four potential technologies. These technologies are to be used as power plants that are considered "clean" energy. The estimated energy output of these plants were calculated and the resources needed to run these were also listed.
In a desert region, which two technologies can possibly be used?
B and D
A and C
A and B
A and D
A and B
In a desert area there is no access to water. Therefore any technologies involving the use of water cannot be used efficiently if at all. This leaves the technologies that only require the sun or wind. The correct answer is therefore A and B.
Example Question #1144 : Act Science
A student conducts an experiment in which she suspends a ball mass 
At one point in the student's experiment, 
The correct answer is is 10N. First, let's ignore the variables as they are unnecessary information. Next, since we are halving the velocity, we have to divide the original force by four. Then, we multiply the new force by two since we are doubling the mass. The radius is staying the same. Therefore, our predicted force should be 
Example Question #1144 : Act Science
A student conducts an experiment in which she suspends a ball mass 
What is the relationship between the force in the string and the mass of the ball?
Negative, exponential relationship
Negative linear relationship
No discernible relationship
Positive linear relationship
Positive exponential relationship
Positive linear relationship
The correct answer is that it is a positive, linear relationship. As we can see in the equation, 
Example Question #22 : Physics
A student is performing a science experiment for his class. The student creates a ramp that contains four different surfaces, carpet, glass, wood and plastic. The ramp is held at a constant angle and a ball is allowed to roll down the ramp. The student tests each material by releasing a ball at different distances from the bottom of the ramp and recording the time it takes for the ball to travel the distance of the ramp.
What is the slowest material that the student tested?
Carpet
Plastic
Wood
Glass
Carpet
The slowest surface is the one that causes the most time for the ball to travel down the ramp. It can be seen that at all distances the carpet takes a longer time to travel down the ramp. The slowest surface was the carpet.
Example Question #22 : Physics
Metal wires are often used to conduct electricity. The electricity that flows through a wire is measured as "current." Therefore, a wire with an electric current is called a current carrying wire.
Current carrying wires also have a tendency to produce magnetic fields that circulate around them. The strength of that magnetic field is determined by the following equation where 
If a wire has a magnetic field of 
The correct answer is 
Example Question #1146 : Act Science
Sometimes scientists need to scale down experiments because collecting full-scale data may not be practical or possible. Most of the time, the data collected during a small scale-experiment is an accurate indicator of full-scale results. For example, research of craters on the Earth’s surface has indicated that the Earth has experienced a history of massive meteor collisions. It has been hypothesized that, amongst other things, these impacting meteorites caused the Earth’s oceans to vaporize. The detrimental effects associated with meteor collisions would have made the planet to be uninhabitable to humans. Due to these adverse effects, an experiment that could produce meteor-sized craters would not be possible in a full-scale setting.
Researchers have developed small-scale experiments that are exemplary of Newton’s three laws of motion. Newton’s first law states that an object in motion will stay in motion unless it is acted on by another force. This phenomenon is known as inertia. The second law comes in the form of an equation that calculates how much force is exerted on two colliding objects with respect to mass and acceleration. In other words force is equal to the mass of an object multiplied by its acceleration. The third law states that for every action there is an equal and opposite reaction. In other words, forces always occur in pairs. A counter force that is equal in magnitude and opposite in direction compliments each force in a particular direction. For example, if you push downwards on a table then the table, in theory, pushes upwards with the same force.
In a particular small-scale exercise, students were asked to design an experiment in which two “meteorites” would be dropped into a medium of sand and the subsequent crater diameters would be measured. Afterwards, the sand would be leveled and the experiment would be repeated. The students were asked to identify all of the factors that could affect the formation of the craters. This was done in order to ensure that each experiment was testing one independent and one dependent variable at a time. Otherwise, it would be unclear which variable is causing the observed effect. Possible variables that could alter the outcome of the experiment included but were not limited to the following: height of the fall, speed of the “meteorite,” angle of impact, and the mass of meteorite.
Consider an experiment that seeks to identify the mass of the meteorite analog. All other variables would have to remain constant in order to ensure accurate results. In order to do this, the height of the fall was set to one meter. The object was placed on top of a vertical meter stick. In order to keep the acceleration and height of the drop constant, it was rolled off of the stick instead of being pushed or simply dropped. Last, a protractor was used to keep the meter stick at a ninety-degree angle. In the procedure, a marble and a golf ball were used as “meteorites” of different masses.
The results of the experiment were recorded in the table and figure provided.
| Crater Diameter (cm) | ||
| Trial Number | ||
| Marble (mass = 4g) | Golf ball (mass = 46g) | |
| 1 | 4.5 | 7.75 |
| 2 | 4.5 | 6 |
| 3 | 4 | 5.5 |
| 4 | 3 | 6 |
| 5 | 3 | 6.5 |
| 6 | 3.5 | 7 |
| 7 | 3 | 5 |
| 8 | 3 | 5 |
| 9 | 3 | 7 |
| 10 | 3.5 | 6 |
| Average | Average | |
| 3.5 cm | 6.175 cm | |
Predict what would happen to the crater size if the experiment changed the velocity instead of the mass of the objects.
The craters would grow in size exponentially as the velocity increases.
The crater sizes would follow a similar pattern of growth as the mass based experiment.
The craters would get smaller as the velocity increases whereas the craters increased in size when mass increased.
Not enough information is given to make a prediction about the experiment.
The craters would grow in size exponentially as the velocity increases.
Since kinetic energy has an exponential relationship with velocity, the craters would grow exponentially in size as the velocity increases. This is because the amount of force increases in the same fashion; therefore, we know that an impact zone is affected more by an object’s velocity than its mass.
Example Question #1 : How To Find Experimental Design In Physics
Laura is performing an experiment with a 5kg weight tied to a 3m rope tied to the ceiling as shown: 
Laura drops the weight and allows it to swing freely. She measures how long it takes for the weight to return to it's original position (assume no forces outside of gravity are acting upon the pendulum). This is also called one oscillation.
Experiment 1:
Laura created the following table for her first measurement of the pendulum's oscillations.
Experiment 2:
Laura performed the experiment again, this time using a 6kg weight.
Experiment 3:
Laura performed the experiment again, this time using a 3kg weight and a 5m rope.
Jerry reads about this experiment, and attempts to recreate the experiment at home. He observes that when he lets go of the pendulum, it never reaches its original height. It gets close, but never fully reaches it. Why?
Jerry did not tie the pendulum to the ceiling.
Jerry is using the wrong length of rope.
External forces acting on the pendulum.
Jerry is using the wrong weight.
External forces acting on the pendulum.
In the set up of the problem, it is stated that no forces outside of gravity (such as friction, air resistance, etc.) are acting upon the weight. If those forces also act upon the pendulum, then Jerry's results would be correct.
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