Answer:
140 watt
Step-by-step explanation:
We are given that
Force applied by student ,F=28 N
Weight pulled by students=70 N
Displacement,s=15 m
Time=3 s
We have to find the power developed by the student.
Work done=w=

Work done by the student=

Power=

Using the formula
Power=

Hence, the power developed by the students=140 watt