Whateverchan
New member
- Joined
- Oct 18, 2013
- Messages
- 13
1. The height (in meters) of a projectile shot vertically upward from a point 4 m above ground level with an initial velocity of 25.5 m/s is h = 4 + 25.5t − 4.9t^2 after t seconds. (Round your answers to two decimal places.)
So, I found its velocity, maximum height, and how long it takes to reach the maximum height. What I have to do now is find out when it would hit the ground and with what velocity.
For how long it would hit, I am supposed to set 4 + 25.5t − 4.9t^2 = 0, and solve for t. But I am not sure how to tackle this one, because all problems I've seen only have a number with t^2 and another constant. That 25.5 throws me off. As for velocity, I think I just to plug the new found t into the original equation. What do I do?
2. A stone is dropped into a lake, creating a circular ripple that travels outward at a speed of 60 cm/s. Find the rate at which the area within the circle is increasing after each of the following. 1s, 3s, 7s.
I found the derivative of the area of the circle to be 2pi r. I just have to multiply 60 with the number of seconds, and plug it into the derivative, correct? Well I tried that, for example, 1s would be 120pi or 277, and they both came out wrong. What did I miss?
So, I found its velocity, maximum height, and how long it takes to reach the maximum height. What I have to do now is find out when it would hit the ground and with what velocity.
For how long it would hit, I am supposed to set 4 + 25.5t − 4.9t^2 = 0, and solve for t. But I am not sure how to tackle this one, because all problems I've seen only have a number with t^2 and another constant. That 25.5 throws me off. As for velocity, I think I just to plug the new found t into the original equation. What do I do?
2. A stone is dropped into a lake, creating a circular ripple that travels outward at a speed of 60 cm/s. Find the rate at which the area within the circle is increasing after each of the following. 1s, 3s, 7s.
I found the derivative of the area of the circle to be 2pi r. I just have to multiply 60 with the number of seconds, and plug it into the derivative, correct? Well I tried that, for example, 1s would be 120pi or 277, and they both came out wrong. What did I miss?