How to Calculate Algebra problems

[Blue22]

I'm taking a computer science class that deals mostly with coding. I'm terrible at stuff like this but it's a graduation requirement (even though my major has nothing to do with this) So I might as well start learning.

One of our assignments has two questions that I wouldn't even begin to know how to answer. I have to write a program that solves these two equations

1) F = K (M1M2)/d^2

K = 6.67 * (10^-11 * m^3 * kg^-1 * m^-2)

I need to write a program that prompts the user to input the masses of the bodies and the distance between the bodies, and then outputs the force between the bodies.


2) (ax + b)(cx + d)

this one seems simpler. I just need the program to solve these problems using the FOIL method, letting the user input the values for a, b, c, and d


If anyone could help me understand how to write these programs, I'd really appreciate it :)

[Zhuge]

These are actually very simply to write; you only need how to prompt the user for input and how to assign to a variable (the formulas you have will almost work just copied in to code - just remove the units and rewrite the squaring portions).

What kind of program can you write? I'd like to know what point I need to explain from.

[Blue22]

The only programs I've been able to write are like the most basic of basic programs. Like that "Hello World" one. We haven't really gotten very far in the class. I use VisualStudio Express if that helps

[Blue22]

Sorry. I don't mean to rush but this is for an assignment that's due tomorrow.

[giblit]

Well you have the equations already. To get input you use cin >> instead of cout << so simply get the input then assign the values to a variable and output the values. Though keep in mind that an integer/integer = integer but if you make one a floating point(float or double) it will result in a floating point (float or double). You can do this by casting with (type) where type is float or double or static_cast<type>(variable or value) or adding a '.', '.0' or '.f' to the end of the value. Though these shouldn't really be a problem when dealing with masses/distances.

I'm sure you already know what the multiply and divide operators are so you would do something like:

double mass1 = 0.0;
double mass2 = 0.0f;

//get the input using cin >>

double k = 6.67 * 0.00000000001 * mass1 * masss1 * mass1 * weight / 10.0 * mass1 * mass1 / 100.0; //who knows which mass m is :P 

and then you would do the same for the rest of it.

Good luck on the assignment :) I probably won't be able to help you more unless it's due in more than 20 hours.

[Blue22]

Thanks. This definitely helps and I kind of have but most of this stuff feels like an alien language. Here's my attempt but Visual Studio is telling me I'm doing something wrong.

#include <iostream>

using namespace std;

int main()
{


	double m1;
	double m2;
	double d;
	double k = 6.67 * (10 ^ -11 * m^3 * kg^-1 * m^-2);


	cout << "Mass of the first person" << endl;
	cin >> m1;

	cout << "Mass of the second person" << endl;
	cin >> m2;

	cout << "Distance between bodies" << endl;
	cin >> d;

	double Force = k*((m1*m2 / d ^ 2));
	cout << Force << endl;

	system("pause");

	return 0;



}

That's about all I really know how to do

[JoshuaMostafa]

First and foremost, your formula for calculating the gravitational force between two objects is wrong :)

This program should work just fine. It also has the right formula.
The second program is way simpler using the same fashion. This one is in fact a piece of cake too.

Please try to learn by doing (that's the purpose of the assignment I guess).

#include<iostream>

using namespace std;
 
int main()
{
    double mass1, mass2, k, result; 
    k = 6.674 * 0.00000000001; 
    
    cout << "enter the mass of the first object" << endl;
    cin >> mass1;
    
    cout << "enter the mass of the first object" << endl;
    cin >> mass2;
    
    cout << "enter the distance between the objects" << endl;
    cin >> d;
    
// your formula for gravitational force calculation is wrong. This is the right one :)
    result = (k * mass1 * mass2) / (d * d); 
    
    cout << "The gravitational force is: " << result <<" N" << endl;
    
    system("pause");
    
	return 0;
}

Post a reply if you need help with the second one AFTER YOU TRY YOURSELF.

[JoshuaMostafa]

This is wrong:
K = 6.67 * (10^-11 * m^3 * kg^-1 * m^-2)

You should not have included unites in the K constant. Its G actually, not K.

http://www.school-for-champions.com/science/gravitation_force_objects.htm#.VCTiTfldW1c

C++ does not care nor understand unites in this case!

[Blue22]

I used K because that's what my teacher had instead of G :/

[mutexe]

('k' is often used as the constant of proportionality symbol when talking in a general context).

[Blue22]

I was able to get some help from a friend last night. He was able to walk me through it and I have a much better understanding now :)

#include <iostream>
#include <math.h>
using namespace std;

int main()
{


	double m1;
	double m2;
	double d;
	double k;
	k = (6.67 * pow(10, -11));

	std::cout.precision(2);

	cout << "Mass of the first person" << endl;
	cin >> m1;

	cout << "Mass of the second person" << endl;
	cin >> m2;

	cout << "Distance between bodies" << endl;
	cin >> d;

	cout << "The Force is: " << endl;

	float Force = k*((m1*m2) / pow(d, 2));
	cout << std::scientific << Force << " * m^3 * kg^-1 * m^-2" << endl;

	return 0;



}

#include <iostream>
using namespace std;

int main()
{
	int A, B, C, D;

	cout << "(Ax*B)(Cx*D)" << endl;

	cout << "Input the value of A: ";
	cin >> A;
	cout << "Input the value of B: ";
	cin >> B;
	cout << "Input the value of C: ";
	cin >> C;
	cout << "Input the value of D: ";
	cin >> D;

	cout << (A*C) << "x^2 + " << (A*D + B*C) << "x + " << (B*D) << endl;

	return 0;
}

[TheIdeasMan]

One lots of small things .....

const double k = 6.67e-11; // double value with exponent

Remember, one must always specify a type (double in this case)

Also, the pow function is rather expensive, because it uses a series expansion to do it, so only use it if the exponent is not an integer. So d squared is just d * d

Always initialise your variables with something when you declare them - this can be the biggest source of errors.

Don't have using namespace std; Google why this is so.

Hope all is well :+)