Free Scientific Reasoning MCQs with Answers

131. If the given crank shaft moves clockwise, then in which directions will the alternator and the fan move?

• A. Both move anti-clockwise.
• B. Anti-clockwise and clockwise respectively.
• C. Clockwise and anti-clockwise respectively.
• D. Both move clockwise.

Explanation: In a typical mechanical setup with gears, the direction of movement is determined by the engagement of these gears. When the crankshaft moves clockwise, it typically drives the alternator directly in the same direction. The fan, however, is often connected through another gear, causing it to move in the opposite direction, i.e., anti-clockwise. Therefore, Option C is correct. Options A and D are incorrect because they suggest that both components move in the same direction, which is not typical in this scenario. Option B suggests an unusual gear setup that isn't normally used.

132. Why is copper used in household wiring?

• A. High resistivity
• B. Magnetic properties
• C. Good conductivity and ductility
• D. Reacts with water

Explanation: Copper is used in household wiring primarily because of its excellent electrical conductivity and ductility. These properties allow it to efficiently carry electric current and be easily shaped into wires. In contrast, materials with high resistivity hinder electrical flow, magnetic properties are irrelevant for non-magnetic copper in wiring, and reactivity with water would make a material unsuitable for durable electrical applications.

133. The rise of mercury in a thermometer is due to:

• A. Gravity
• B. Thermal expansion
• C. Condensation
• D. Capillary action

Explanation: The rise of mercury in a thermometer is primarily due to thermal expansion. When mercury is heated, it expands and takes up more space, causing it to rise within the narrow tube of the thermometer. This phenomenon is used to measure temperature changes. The other options are incorrect: Gravity doesn't influence the rise of mercury in this context; Condensation involves a phase change from gas to liquid, unrelated to mercury's behavior; and Capillary action refers to liquid movement in narrow spaces due to surface tension, not affecting thermometer readings.

134. If the 3 trials could be run simultaneously on parallel setups, in what order, from first to last, would the carts get to point B?

• A. Trial 1, Trial 2, Trial 3
• B. Trial 3, Trial 2, Trial 1
• C. Trial 2, Trial 1, Trial 3
• D. Trial 3, Trial 1, Trial 2

Explanation: The correct order is Trial 3, Trial 2, Trial 1 because when running trials simultaneously on parallel setups, Trial 3 will reach point B first, followed by Trial 2 and then Trial 1. The incorrect options either ignore the concept of simultaneous trials or misplace the order of the trials.

135. Mass is added to the cart by the addition of a wooden block that rests on top of it. When the force is increased to 4.0 newton's, the block falls off as the cart begins to accelerate. Why does it fall off when the force is increased to this level?

• A. The force accelerating the cart becomes large enough so that the force of friction holding the block in place is overcome
• B. The force of friction holding the block in place becomes large enough to overcome the force accelerating the cart
• C. The mass of the cart becomes too large, and the load must be reduced for the cart to accelerate
• D. The acceleration becomes nonuniform with this force

Explanation: When the force applied reaches 4.0 newtons, the added mass of the block increases the total mass of the cart. This increase in mass requires a reduction in load for the cart to accelerate effectively, causing the block to fall off. The other options are incorrect because they do not accurately describe the relationship between force, mass, and acceleration in this specific situation.

136. Another experiment showed the velocities for a trial to be 1.0 m/s, 2.5 m/s, 4.5 m/s, and 7.0 m/s when measured at the same time. What trend occurred in the average acceleration?

• A. It was constant
• B. It decreased by 10.0 m/s2 each interval
• C. It decreased by 5.0 m/s2 each interval
• D. It increased by 5.0 m/s2 each interval

Explanation: The correct answer is Option B: It decreased by 10.0 m/s2 each interval. This is because the velocities increased from 1.0 m/s to 2.5 m/s (an increase of 1.5 m/s), then from 2.5 m/s to 4.5 m/s (an increase of 2.0 m/s), and finally from 4.5 m/s to 7.0 m/s (an increase of 2.5 m/s). The differences between these velocities indicate a decreasing trend in average acceleration. The other options are incorrect as they do not accurately reflect the relationship between the velocities and acceleration as described in the experiment.

137. If Trial 3 were redone with a force of 1.0 newton, then compared to that found in Trial 3, the average acceleration would be:

• A. Initially lower and decreasing
• B. Initially lower and constant
• C. The same
• D. Initially higher but decreasing

Explanation: The correct answer is Option A: Initially lower and decreasing. When redoing Trial 3 with a force of 1.0 newton, the average acceleration would likely be lower than the original acceleration in Trial 3 due to the lower force applied. Additionally, as the force remains constant, the acceleration would be expected to decrease over time. Option B, C, and D do not accurately reflect the relationship between force and acceleration in this scenario.

138. A student studied the relationship between the current,voltage,and resistance in a direct circuit.To obtain the results presented in Figure 1 and Table 1,the student constructed the circuit shown below.The student used 3 resistors and different amounts of voltage generate Table 1.The current was read from the ammeter.To obtain the results in Table 1,a 5-ohm resistor (Resistor 4)was used varid .The current was measured at the power was then calculated.Acocording to Figure 1, when 6V were applied to Resistor 1,the current was:

• A. 0.50amp
• B. 0.75amp
• C. 1.50amp
• D. 2.25amp

Explanation: The correct answer is Option D: 2.25amp. When 6V are applied to Resistor 1 with a resistance of 3 ohms, the current can be calculated using Ohm's Law (I = V/R), resulting in 2.25 amps. The other options provided incorrect calculations of current based on the given circuit parameters.

139. A student studied the relationship between the current,voltage,and resistance in a direct circuit.To obtain the results presented in Figure 1 and Table 1,the student constructed the circuit shown below.The student used 3 resistors and different amounts of voltage generate Table 1.The current was read from the ammeter.To obtain the results in Table 1,a 5-ohm resistor (Resistor 4)was used varid .The current was measured at the power was then calculated.If a headlight uses 150 W and the car's battery produces 12 V, what is the current in the circuit?

• A. 1.25 amp
• B. 12.5 amp
• C. 12.00 amp
• D. 25.00 amp

Explanation: The correct answer is Option A: 1.25 amp. By using the formula P = IV and substituting the given values for power (150 W) and voltage (12 V), we can calculate the current as I = P/V = 150 W / 12 V = 1.25 A. The other options provide incorrect calculations or rounding errors based on the same formula.

140. A student studied the relationship between the current,voltage,and resistance in a direct circuit.To obtain the results presented in Figure 1 and Table 1,the student constructed the circuit shown below.The student used 3 resistors and different amounts of voltage generate Table 1.The current was read from the ammeter.To obtain the results in Table 1,a 5-ohm resistor (Resistor 4)was used varid .The current was measured at the power was then calculated. If a trial had been performed using Resistor 3 and 12 V, the current would have been:

• A. 1.25 amp
• B. 1.75 amp
• C. 2.25 amp
• D. 2.80 amp

Explanation: The correct answer is 1.25 amp. By applying Ohm's Law (V = IR) and considering the resistor value of 3 ohms and voltage of 12 V, the current can be calculated as 12V / 3 ohms = 4 amp. Since this calculation is for Resistor 3, the total current would be 4 amp / 3 resistors = 1.25 amp. The other options provided do not match the correct calculation based on the given values in the question.