A = -9.8
v = -9.8t -8
s = -4.9 t2 -8t +25
So… -5t^2 -8t + 25 =0, we’ll rearrange to 5t^2 + 8t - 25. We get two roots, one is positive and is 1.59 seconds
V = -9.8(1.59) - 8 = -23.6
So… it takes 1.59 seconds to hit the ground at -23.6 m/s.
The third option is wrong
Answer:
Average force = 67 mn
Explanation:
Given:
Initial velocity u = 0 m/s
Final velocity v = 67 m/s
Time t = 1 ms = 0.001 sec.
Computation:
Using Momentum theory
Change in momentum = F × Δt
(v-u)/t = F × Δt
F × 0.001 = (67 - 0)/0.001
F= 67,000,000
Average force = 67 mn
Answer:
acceleration a = 1.04 m/s2
Explanation:
Assume the train has a speed of 23m/s when the last car passes the railway workers. Once this happens the last car would have traveled a total distance of the 180m distance between the railway worker standing 180 m from where the front of the train started plus the 75m distance from the first car to the last car:
s = 75 + 180 = 255 m
We can use the following equation of motion to find out the distance traveled by the car:
where v = 23 m/s is the velocity of the car when it passes the worker,
= 0m/s is the initial velocity of the car when it starts, a m/s2 is the acceleration, which we are looking for.


