iGCSE Physics (0625) 1.7.2 Work-Exam Style Questions- New Syllabus
▶️ Answer/Explanation
Detailed solution:
Mechanical work done is defined as the product of the force applied and the distance moved in the direction of that force.
The formula for calculating work done is $W = F \times d$, where $F$ represents the size of the force and $d$ represents the distance moved.
While the time for which a force acts is used to calculate power ($P = \frac{W}{t}$), it is not required to determine the total work done.
According to the provided table, row B correctly identifies that the force and distance are needed ($\checkmark$), while time is not ($X$).
Therefore, only the size of the force and the distance it moves the object are necessary for this calculation.
▶️ Answer/Explanation
Detailed solution:
According to the principle of conservation of energy, the total energy in a system remains constant.
The initial gravitational potential energy ($\Delta E_{p} = 46 \text{ J}$) is transferred as the stone falls.
Part of this energy is used to do work against air resistance ($W = 21 \text{ J}$), which is dissipated as thermal energy.
The remaining energy is converted into the stone’s kinetic energy gain ($\Delta E_{k}$).
Using the equation: $\Delta E_{p} = \Delta E_{k} + W$, we find $\Delta E_{k} = 46 \text{ J} – 21 \text{ J}$.
Therefore, the gain in kinetic energy is $25 \text{ J}$.
▶️ Answer/Explanation
Detailed solution:
Mechanical work done is defined as the product of the force applied and the distance moved in the direction of the force.
The mathematical formula is expressed as $W = Fd$, where $W$ is work, $F$ is force, and $d$ is distance.
Time is only required for calculating power ($P = \frac{W}{t}$), not for the total work done itself.
Therefore, to find the work done while pushing the mower, the woman only needs to know the force exerted and the distance covered.
This makes Option B the correct choice as it identifies both necessary variables without including irrelevant quantities.