Totally confused on this question, Please help.
1)In the movie The avengers, Captain America sees an alien speeder incoming. The speeder passes directly overhead at 3.65m. If he throws his shield straight up with a speed of 7.40 m/s from a height of 1.55 m above the ground (a) will the shied reach the speeder? (b) if so, what velocity? If not, what initial speed must it have to reach the speeder? (c) Find the change in speed of the shield if it were thrown straight down from the speeder to 1.55 m with an initial speed of 7.40 m/s. (d) Does the change in speed of the downward-moving shield agree with the magnitude of the speed change of the shield moving upward between the same elevations? (e) Explain physically why it does or does not agree.
a. d1 = 3.65-1.55 = 2.10 m. = Distance the shield must travel.
V^2 = Vo^2 + 2g*d2 = 0.
2g*d2 = -Vo^2, d2 = -Vo^2/2g = -(7.4)^2/-19.6 = 2.79 m. Yes.
b. V^2 = 7.4^2 - 19.6*2.10 = 13.6, V = 3.69 m/s.
7.4 - 3.69 = 3.71 = Change in speed.
c. V^2 = 7.4^2 + 19.6*2.1 = 95.92, V = 9.79 m/s.
9.79-7.4 = 2.39 m/s = The change in speed.
d. No.
e. When the shield is moving upward, the force of gravity decreases the speed. When the shield is moving downward, the force of gravity increases the speed.
To solve this problem, let's break it down into smaller parts:
(a) Will the shield reach the speeder?
To answer this question, we need to compare the height of the speeder (3.65 m) with the initial height of the shield (1.55 m). If the shield's height is greater than or equal to the speeder's height, then the shield will reach the speeder. Otherwise, it won't.
In this case, the shield's initial height is 1.55 m, which is less than the speeder's height of 3.65 m. Therefore, the shield will not reach the speeder.
(b) If the shield does reach the speeder, what velocity?
Since the shield does not reach the speeder, we don't need to calculate the velocity.
(c) Find the change in speed of the shield if it were thrown straight down from the speeder to 1.55 m with an initial speed of 7.40 m/s.
To find the change in speed, we can use the equation:
Δv = vf - vi
Here, vf is the final velocity and vi is the initial velocity.
When the shield is thrown straight down, the final velocity (vf) would be its initial velocity (since it's thrown with a constant speed). Therefore, the change in speed would be:
Δv = vf - vi = 7.40 m/s - 7.40 m/s = 0 m/s
The change in speed would be 0 m/s, meaning there is no change.
(d) Does the change in speed of the downward-moving shield agree with the magnitude of the speed change of the shield moving upward between the same elevations?
Since the change in speed of the downward-moving shield is 0 m/s, we need to compare it with the magnitude of the speed change of the shield moving upward.
The speed change of the upward-moving shield can be calculated using the equation:
Δv = vf - vi
Here, vf is the final velocity and vi is the initial velocity.
Since the shield doesn't reach the speeder, the final velocity would be 0 m/s. The initial velocity was 7.40 m/s. Therefore, the speed change would be:
Δv = 0 m/s - 7.40 m/s = -7.40 m/s
The magnitude of the speed change is 7.40 m/s.
(e) Explain physically why it does or does not agree.
The change in speed of the downward-moving shield is 0 m/s, while the magnitude of the speed change of the shield moving upward is 7.40 m/s. This difference arises because when the shield is thrown upward, it loses speed due to the influence of gravity. On the other hand, when the shield is thrown downward, it gains speed due to the same gravitational force.
In other words, the gravitational force acts as an opposing force to the upward motion, thus causing a decrease in speed. However, when the shield is thrown downward, the gravitational force acts in the same direction as the motion, resulting in an increase in speed. Therefore, the change in speed in the upward and downward motions of the shield is not the same.