Answer:
7.4375N
Explanation:
According to Newtons second law
F = ma
m is the mass = 140g = 0.14kg
Get the acceleration
v = u + at
8.5 = 0+0.1a
a = 8.5/0.16
a = 53.125m/s²
Get the required force
F = 0.14 * 53.125
F = 7.4375N
Hence the magnitude of the average force on the wall is 7.4375N