# Projectile motion with drag. Im not sure what Im doing wrong here but it tells me my matrix dimensions must agree however I thought that if I use .* it can multiply a scalar and a vector together

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답변: Image Analyst 20 Dec 2020
function projectile_golf
clear
clc
format long g;
workspace
format compact
fontSize = 20;
g = 9.81; % acceleration due to gravity in Y
y0 = 0; % intial position y
v0 = 50; % initial velocity magnitude
Angular_w = 100; % Angular Velocity (rad/s)
angle = 30; % angle of strike
c = 4.5*10^(-5); % Coefficient of drag
r = 21.5*10^(-3); % Radius of gold ball
m = 46*10^(-3); % Mass of golf ball
rho_air = 1.2; % Density of air
dt=0.1;
t=[0:dt:200];
v(1) = v0; % Velocity Magnitude
Vel = [v0*cosd(angle),v0*sind(angle)- g*t,0]; % Velocity Vector
FdragX(1) = v(1).*Vel(1).*c; % Drag force in X direction
FdragY(1) = v(1).*Vel(1).*c; % Drag force in Y direction
p = [0,0,0];
AccDrag = [FdragX(1)./ m, FdragY(1)./ m, 0]; % F=M*A decceleration due to drag
for i=2:length(t)
v(i) = sqrt((Vel(1)^2)+(Vel(2)^2));
p(i) = p(i-1) + Vel.*t - AccDrag.*(t^2);
v(i) = v(i-1);
Vel = [v(i)*cosd(angle),v(i)*sind(angle)- g*t,0];
FdragX(i) = v(i).*Vel(i).*c;
FdragY(i) = v(i).*Vel(i).*c;
AccDrag(i) = [FdragX(i)./m, FdragY(i)./m, 0];
end
plot(p)

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### 채택된 답변

Image Analyst 20 Dec 2020
Perhaps you need to index all vectors by i
p(i) = p(i-1) + Vel.*t - AccDrag.*(t^2);
Vel and t are vectors, so try
p(i) = p(i-1) + Vel(i).*t(i) - AccDrag.*(t(i)^2);
AccDrag is a 3 element vector. I'm not sure which of the 3 values you want to use.

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