Why did the civil war / 13th amendment and women's right to vote / amendment 19 happened?

(a)

Let:

a be the acceleration of the system,

g be the acceleration due to gravity,

T be the tension in the string.

For mA:

T = mA a

For mB:

mB g - T = mB a

Adding to eliminate T:

mB g = (mA + mB) a ... (1)

a = mB g / (mA + mB)

= 7.0 * 9.81 / (11.0 + 7.0)

= 3.815 m/s^2

= 3.82 m/s^2 to 3 sig. fig.

(b)

Let:

s be the distance to the edge of the table,

t be the time taken.

s = at^2 / 2

t = sqrt (2s / a)

= sqrt (2 * 1.250 / 3.815)

= 0.810 sec to 3 sig. fig.

(c)

From (1):

(mA + mB) (a / g) = mB

mA (a / g) = mB (1 - a / g)

mA = mB (g / a - 1)

= 4.0 (100 - 1)

= 396 kg.