The work done on the backpack by the student applies 80 N of force to lift the backpack 1.5 m is 120J.
<h3>How to calculate work done?</h3>
Work done is a measure of energy expended in moving an object; most commonly, force times distance.
It is said that no work is done if the object does not move, hence, the work done on an object can be calculated as follows:
Work done = Force × Distance
According to this question, a student carries a very heavy backpack and to lift the backpack off the ground, the student must apply 80 N of force to lift the backpack 1.5 m.
Work done = 80N × 1.5m
Work done = 120J
Therefore, the work done on the backpack by the student applies 80 N of force to lift the backpack 1.5 m is 120J.
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Answer:

Explanation:
The initial velocity, u, of the car=15m/s
The final velocity, v, of the car =0m/s
Time, t, taken for the car to come to a stop=5s
Acceleration is calculated by,

By substitution,



The negative sign implies that the car has decelerated.
The gravity of Earth, denoted by g, is the net acceleration that is imparted to objects due to the combined effect of gravitation and the centrifugal force. In SI units this acceleration is measured in metres per second squared or equivalently in newtons per kilogram.
The answer is C. Because energy cannot be created or destroyed