Answer:
After 9 seconds the object reaches ground.
Step-by-step explanation:
We equation of motion given as h = -16t²+128t+144,
We need to find in how many seconds will the object hit the ground,
That is we need to find time when h = 0
0 = -16t²+128t+144
16t²-128t-144= 0

Negative time is not possible, hence after 9 seconds the object reaches ground.
Answer:
I think -7 N. Netforce is 3N-10N= -7N
Explanation:
The μs between the clock and floor is 650(M*g) and the μk between the clock and the floor is 560(M*g)