An electron is trapped in a square well of unknown width, L. It starts in unknown energy level, n. When it falls to level n-1 it

Answer:

W = 294 J

Explanation:

provided,

mass of the projectile = 2 Kg

horizontal displacement = 20 m

vertical displacement = 15 m

work performed by the gravitational force =?

the work done by gravitational force only accounts for vertical motion.

force due to gravity =  m g

= 2 x 9.8 = 19.6 N

work is equal to force x displacement

W = F x s

W = 19.6 x 15

W = 294 J

A hiker proceeds 200 m west and subsequently another 100 m north, resulting in a displacement of 223 m. The direction can be determined using the trigonometric function where sin(angle) = opposite/hypotenuse, yielding an angle of 26.6 degrees. Therefore, the total displacement is 223 m at an angle of 26.6 degrees north of west.

Part A: -,+

The elevator descends, dictating the velocity's direction, which aligns with the movement's path. With the positive direction defined as upward, the velocity is negative. After the emergency button is pressed, the elevator begins to stop, indicating that the velocity is decreasing. Therefore, the acceleration is oriented in the opposite way to the velocity, making its sign +.

Part B: +, -

The ball ascends, which determines the positive direction of the velocity. Hence, the velocity is positive.

Once the ball is thrown, the only force acting on it is gravity, opposing the ball’s ascent and causing it to descend. This means the acceleration is directed downwards, resulting in a negative sign.

Part C: 0, -

Throughout the ball's trajectory from the moment it's thrown until it drops to the ground, gravity constantly exerts downward acceleration (-).

After the throw, the ball's velocity will decline due to gravity. When it reaches a velocity of 0, it achieves its peak height. At this specific moment, the ball begins to descend again under the influence of gravity. However, at the peak height, the ball's velocity is 0.

Answer:

change in KE = -12.95 Btu

Explanation:

provided data

mass = 3000-lbm

initial velocity of vehicle vi = 10 mph = 14ft/s

final velocity of vehicle vf = 0 mph = 0 ft/s

solution

the crumple zone is designed to absorb kinetic energy upon impact

thus the change in KE is related to the initial and final speeds, expressed as:

change in KE = 0.5 × m × (vf² - vi² ).................1

Substituting in the parameters yields:

change in KE = 0.5 × 3000 × (0² - 14.7² )

change in KE = -324135 × *  

change in KE = -12.95 Btu

Set the initial location of kitten A on the left side of the field (designated as point A) at the origin, running east which is the positive direction. Kitten B starts at position , while kitten A’s beginning spot is .

Kitten A moves with a velocity of , and kitten B with . Their positions over time are described by

The collision occurs when the positions are the same, i.e. when . Solving this gives

Which results in approximately 6.8 seconds, considering significant figures.