Explanation:
Given that,
Initial speed of the electron, 
Distance, s = 5 cm = 0.05 cm
Acceleration of the electron,
(a) Let v is the electron's velocity when it emerges from this region. It can be calculated as :


v = 871779.788 m/s
or

(b) Let t is the time for which the electron take to cross the region. It can be calculated as:



Hence, this is the required solution.
Weight equals mass times gravitational acceleration=400N, so mass=400/9.8=41kg approx.
Let Karen's forward speed be considered as positive.
Therefore, before the headband is tossed backward, the speed of the headband is
V = 9 m/s
The headband is tossed backward relative to Karen at a speed of 20 m/s. Therefore the speed of the headband relative to Karen is
U = -20 m/s
The absolute speed of the headband, relative to a stationary observer is
V - U
= 9 + (-20)
= - 11 m/s
Answer:
The stationary observes the headband traveling (in the opposite direction to Karen) at a speed of 11 m/s backward.
Answer:
In your question which ask to design a ballistic spring system to measure the speed of bullet. The ask is to find the expression for the bullets speed by using the term given in your question so base on the data you have given and with my calculation the answer is (M+m)*g*d + 1/2*k*(d1-d)^2