The Flying Cap
A student throws her cap staight upward with a velocity v = 14.7 m/s. How long does it take to reach its highest point. How would I do this problem with just mindlessly using the kinematic equations that were given to me?
Answer
Well, first I would recommend to not be doing physics mindlessly. The most common mistakes come from making assumptions to speed up the problem. That being said, your first step should be finding the equation(s) to use. This problem gives you v_0, a by assumption of gravity, and a distance, so you will want to find an equation or set of equations that has all of these plus t (which you want to solve for). So the best candidate is
x_f=a/2*t^2+v_0+x_0 (x_0 can be assumed to be 0)
However, you don't have an actual value for x_f, so first you need to find that. The hint in this problem is that it is the highest point. At the highest point in a throw, the vertical velocity is 0, so this gives us another variable to use in equation finding. This will lead us to
v_f^2-v_i^2=2*a*(x_f-x_0)
From this we can get x_f in terms of variables we know and then plug the answer back into the first equation. This will give us an equation made of only variables we know and the one we want.
Customer support service by UserEcho
Well, first I would recommend to not be doing physics mindlessly. The most common mistakes come from making assumptions to speed up the problem. That being said, your first step should be finding the equation(s) to use. This problem gives you v_0, a by assumption of gravity, and a distance, so you will want to find an equation or set of equations that has all of these plus t (which you want to solve for). So the best candidate is
x_f=a/2*t^2+v_0+x_0 (x_0 can be assumed to be 0)
However, you don't have an actual value for x_f, so first you need to find that. The hint in this problem is that it is the highest point. At the highest point in a throw, the vertical velocity is 0, so this gives us another variable to use in equation finding. This will lead us to
v_f^2-v_i^2=2*a*(x_f-x_0)
From this we can get x_f in terms of variables we know and then plug the answer back into the first equation. This will give us an equation made of only variables we know and the one we want.