1.

Consider the following statements, regarding a girl who wants to jump vertically upward from a hard horizontal floor. Symbolic representation of forces is given below. vec(F)_(M) = force developed in leg muscles, vec(F)_(W) = Weight, vec(F)_(N) = Normal reaction

Answer»

Total force on FLOOR is `vec(F)_(M)+vec(f)_(w)`.
Resultant force on girl is `(-vec(F)_(M))` while girl is in contact with floor.
Floor exerts a force `vec(F)_(N)` on girl.
The harder the girl pushes down, the greater the resulting acceleration of girl.

Solution :When the girl is bending her LEGS, the total force exerted by her legs in the action, normal force by grand is the reaction. Considering FBD of girl
`vec(F)_(N)+vec(F)_(w)=mvec(a)`
`vec(F)_(N)=-vec(F)_(M)`
So force on floor is `vec(F)_(M)`
Resultant force on giel is `vec(F)_(w)-vec(F)_(M)`
NOTE: If we say the change in force of girl is `vec(F)_(M)`, then (A) and (B) WOULD also be correct.


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