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A student holds a heavy school bag while waiting for the bus without moving. Which of the following statements are correct? (1) Force is applied by the student. (2) The bag is displaced. (3) Work is done on the bag. (4) No work is done in the scientific sense.
and (3) only
and (3) only
, (2), (3)
and (4) only
and (4) only
In physics, work is defined as the product of the force applied on an object and the displacement of the object in the direction of the force. Since the student is stationary, there is no displacement (s=0), which results in zero work done.
In physics, work is defined as the product of the force applied on an object and the displacement of the object in the direction of the force. Since the student is stationary, there is no displacement (s=0), which results in zero work done.
If you push against a concrete wall as hard as you can but it does not budge, you will eventually get tired, but in the eyes of physics, you have performed zero work because the wall remained in its position.
FDS: Force, Displacement, (must have) Synthesis (for work).
W=FтЛЕsтЛЕcos(╬╕) тАФ General work formula
W=0 when s=0 тАФ Condition for zero work
The mathematical expression for work done is W=FтЛЕsтЛЕcos(╬╕), where W is work, F is force, s is displacement, and ╬╕ is the angle between the force and displacement. Because s=0 in this scenario, the work done W must be 0, regardless of the magnitude of the force applied to hold the bag.
Work requires both force and displacement.
If displacement is zero, work done is zero.
Applying force is not equivalent to doing work.
While the student feels exertion due to muscular effort (biological work), this is not 'mechanical work' as defined in physics.
Option B is wrong because work is not done when displacement is zero.
Option C is wrong because displacement did not occur.
D is correct тАФ The student applies a force to counteract gravity, but since the bag undergoes no displacement, the scientific work done is zero.
Always check if the displacement variable (s) is zero in work problems; if it is, the answer is always zero, no matter how large the force (F) is.
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