程序不向函数返回值

我正在尝试制作牛顿第二定律计算器，当我输入计算值时没有任何反应。我不确定它们是否没有返回到主功能还是什么。我想做的是让用户输入一个字符，然后由包含 switch 语句的函数获取，在 switch 语句的情况下，函数调用执行算术的函数，然后这些函数将返回一个值给开关函数，switch 函数将返回一个值给主函数，然后将值打印到屏幕上。

// Newtons2ndlaw.cpp : This file contains the 'main' function. Program 
execution begins and ends there.
//
#include "pch.h"
#include <stdio.h>
#include <stdlib.h>
#include<iostream>
void varselect(char, float *);
void force(float *);
void acceleration(float *);
void mass(float *);
int main()

{
float eqvalue;
char operation;
printf("Welcome to Newtons 2nd law solver!n");
system("PAUSE");
printf("Would you like to solve for a Force, Acceleration or Mass?nType 'F'(for force), 'A'(for acceleration), 'M'(for mass) to select a variablen");
scanf_s("%c", &operation,1);
if (operation == 'f' || operation == 'F' || operation == 'a' || operation == 'A' || operation == 'm' || operation == 'M')           //logic for determing what the user entered
{}
else
{
printf("Please enter a valid character.");
}
varselect(operation,&eqvalue);             //function call to receive float value from varselect function
if (operation == 'f' || operation == 'F')              //{
{
printf("The force = %f",eqvalue);
}
//this block determines what character string to display with calculated float value                                    
else if (operation == 'a' || operation == 'A')                         
{
printf("The acceleration = %f", eqvalue);
}
else if (operation == 'm' || operation == 'M')
{
printf("the Mass = %f", eqvalue);
}
}                                                           //}
void varselect(char x, float *j)                            
//this function recieves the user inputed char value and returns the calculated float value to function call. 
{                                                                   //switch allows program to "understand" users unwillingness to press shift before a,f,m like printf statement tells them to do.
switch (x)                                                      // also allows each variable to call its own function.
{
case 'f':
float getval;
force(&getval);
*j = getval;
return;
break;
}
switch (x)
{
case 'F':
float getval;
force(&getval);
*j = getval;
return;
break;
}
switch (x)
{
case 'a':
float getval;
acceleration(&getval);
*j = getval;
return;
break;
}
switch (x)
{
case 'A':
float getval;
acceleration(&getval);
*j = getval;
return;
break;
}
switch (x)
{
case 'm':
float getval;
mass(&getval);
*j = getval;
return;
break;
}
switch (x)
{
case 'M':
float getval;
mass(&getval);
*j = getval;
return;
break;
}
return;
}
void force(float *fma)                                      
{
float acceleration, mass;
printf("Enter a value for 'Mass', then 'Acceleration'.nn");
scanf_s("%fn%fn", &mass, &acceleration, 2);
*fma = mass * acceleration;
return;
}
void acceleration(float *afm)
{                                                                                                                           //functions to take input from user and return float to varselect function
float force, mass;
printf("Enter a value for 'Force', then 'Mass'.nn");
scanf_s("%fn%fn", &force, &mass, 1);
*afm = force / mass;
return;
}
void mass(float *fam)
{
float force, acceleration;
printf("Enter a value for 'Force', then 'Acceleration'.nn");
scanf_s("%fn%fn", &force, &acceleration, 1);
*fam = force / acceleration;
return;
}