100 nm of work is done over 20 m what force was applied to the object that was moved

HESI A2

HESI A2 Physics Practice Test

1. What force was applied to the object that was moved if 100 Nâ‹…m of work is done over 20 m?

A. 5 N
B. 80 N
C. 120 N
D. 2,000 N

Correct answer: A

Rationale: Work is calculated using the formula Work = Force x Distance. Given that 100 Nâ‹…m of work is done over 20 m, we can rearrange the formula to solve for Force. Force = Work / Distance. Plugging in the values, we get Force = 100 Nâ‹…m / 20 m = 5 N. Therefore, the force applied to the object that was moved is 5 N. Choice B (80 N) is incorrect because it doesn't match the calculated force of 5 N. Choice C (120 N) is incorrect as it is higher than the calculated force. Choice D (2,000 N) is incorrect as it is significantly higher than the correct force of 5 N.

2. Which of the following materials has the lowest density?

A. Water
B. Cork
C. Aluminum
D. Steel

Correct answer: B

Rationale: Cork has the lowest density among the given options. Cork is a lightweight material derived from the bark of cork oak trees and is known for its low density, making it float on water. Water, aluminum, and steel have higher densities compared to cork. Water is denser than cork because it has a consistent density of 1 g/cmÂ³. Aluminum and steel are metals with much higher densities due to their atomic structures, making them denser than cork.

3. The specific heat capacity (c) of a material is the amount of heat transfer (Q) required to raise the temperature (Î”T) of a unit mass (m) of the material by one degree (typically Celsius). The relationship between these quantities is described by the equation:

A. Q = cÎ”T
B. Q = mcÎ”T
C. Q = c / mÎ”T
D. Q = Î”T / mc

Correct answer: A

Rationale: The correct equation relating heat transfer (Q), mass (m), specific heat capacity (c), and change in temperature (Î”T) is Q = mcÎ”T. This equation states that the heat transfer is equal to the product of the mass, specific heat capacity, and temperature change. Therefore, the correct answer is B, as it correctly represents this relationship. Choices C and D do not correctly represent the relationship between these quantities and are therefore incorrect.

4. Which of the following is NOT a mode of heat transfer between a system and its surroundings?

A. Conduction
B. Convection
C. Radiation
D. Isothermalization

Correct answer: A

Rationale: Isothermalization is not a mode of heat transfer. The three main modes of heat transfer are conduction (through direct contact), convection (through fluid motion), and radiation (through electromagnetic waves). In this question, choice A, conduction, is not a mode of heat transfer between a system and its surroundings. Conduction refers to heat transfer through direct contact between particles, without the movement of the particles themselves. Therefore, A is the correct answer. Choices B, C, and D are incorrect as they represent valid modes of heat transfer.

5. Which substance would be most affected by a change in temperature?

A. Liquid nitrogen
B. Salt crystals
C. Hydrogen gas
D. Iron filings

Correct answer: C

Rationale: Hydrogen gas would be most affected by a change in temperature because gases have a greater expansion or contraction in volume with changes in temperature compared to liquids or solids. When the temperature of hydrogen gas increases, its molecules gain kinetic energy and move faster, causing the gas to expand and its volume to increase. Conversely, when the temperature decreases, the gas molecules lose kinetic energy and move slower, leading to a decrease in volume. This property makes hydrogen gas highly sensitive to temperature changes compared to liquid nitrogen, salt crystals, or iron filings. Liquid nitrogen, salt crystals, and iron filings are less affected by temperature changes because their particles are closer together and have lower kinetic energy, resulting in minimal volume changes with temperature fluctuations.