Answer:
v = 79.2 m/s
Solution:
As per the question:
Mass of the object, m = 250 g = 0.250 kg
Angle, 
Coefficient of kinetic friction, 
Mass attached to the string, m = 0.200 kg
Distance, d = 30 cm = 0.03 m
Now,
The tension in the string is given by:
(1)
Also
T = m(g + a)
Thus eqn (1) can be written as:





Now, the speed is given by the third eqn of motion with initial velocity being zero:

where
u = initial velocity = 0
Thus


Answer:
F = 100 Newtons
Explanation:
F = ?
m = 0.04kg
u = 0m/s ==> u is just an abbreviation for initial velocity, it is conventional.
s = 50m ==> s is just an abbreviation for distance, it is conventional.
v = 500m/s ==> v is just an abbreviation for final velocity, it is conventional.

Then F = ma = 0.04 x 2500 = 100N
The answer would be acceleration.
The correct answer should be a
Using Newton's Second Law, F = ma, where F is the net force
So the net force is:
F = (6kg)(4m/s^2) = 24N
Since you are applying a horizontal force of 30N, we can find the force of friction by the difference of the net force and the applied force.
30N-24N = 6N