Computing an equation

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Steven
Steven 2012-2-18
编辑： Azzi Abdelmalek 2013-10-16
I am suppose to find the height and distance traveled by a ball thrown at angle A and a speed v given by:
h(t)=v*t*sin(A)-(1/2)*g*t^2
x(t)=v*t*cos(A)
I am given:
gravity=g=9.81m/s^2
v=10m/s
and the angle A = 35
I know I just plug those into the equations to solve for h(t) and x(t) but I am not given the time "t" so how am I suppose to get t?
I am suppose to compute how high the ball goes, how far it will go, and how long it will take to hit the ground.
PLEASE HELP ME!!!
Part b of the problem asks for "Use the values of v and A given in part a to plot the ball's trajectory; that is, plot h versus x for positive values of h"
How can I do this is we just solved for the exact value of h and x?, we need multiple values of h and x to plot.
  2 个评论
bym
bym 2012-2-18
What do you know about the ball's velocity at the maximum height? What do you know about the ball's height at the time when it hits the ground?
Steven
Steven 2012-2-18
all it gives me is that the velocity is 10 m/s and the gravity and angle that I stated above. I am not given time so how can I figure it out? I know the the answers to the question because they are stated in the back of the book but I don't know how to work my way to the answer. The answers are: ball rises 1.68m high, it will travel 9.58m, and it hits the ground in 1.17s. Those are the answers, hopefully this gives you something to work on.

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回答（2 个）

Krishnendu Mukherjee
make that two functions in function builder.give the time input as a ramp function,f(t)=t;[may t=0:10] add a scope.find the answer
  3 个评论
显示 1更早的评论
Steven
Steven 2012-2-18
The answers to this selected question was posted in the back of my textbook lol
Krishnendu Mukherjee
Krishnendu Mukherjee 2012-2-19
why multiple answer?if u would give a ramp as input.then for different values the different answer would shown as continous signal.you could see.for which value of t maxima is arrising.
why unnecessarily u will make a complicated program?thats why i hv tld that

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Andrei Bobrov
Andrei Bobrov 2012-2-18
syms t
A = 35;
g = 9.81;
v = 10;
h = v*t*sind(A)-(1/2)*g*t^2;
x = v*t*cosd(A);
t_hmax = solve(diff(h,t),t);
hmax = vpa(subs(h,t,t_hmax),5)
x_all = vpa(2*subs(x,t,t_hmax),5)
ADD
xf = matlabFunction(x);
hf = matlabFunction(h);
t2 = linspace(0,2*double(t_hmax),100);
plot(xf(t2),hf(t2))
  2 个评论
Steven
Steven 2012-2-18
Part b of the problem asks for "Use the values of v and A given in part a to plot the ball's trajectory; that is, plot h versus x for positive values of h"
How can I do this is we just solved for the exact value of h and x?, we need multiple values of h and x to plot.
Andrei Bobrov
Andrei Bobrov 2012-2-18
see ADD in my answer

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