In outer space a rock of mass 11 kg is acted on by a constant net force 31, −10, 47 N during a 4 s time interval. At the end of this time interval the rock has a velocity of 110, 80, 105 m/s. What was the rock's velocity at the beginning of the time interval?

98.73 m/s, 83.63 m/s, 87.9 m/s

Explanation:

From the question,

F = m(v-u)/t Equation 1

Where F = Force, m = mass, v = final velocity, u = initial velocity, t = time.

make u the subject of the equation

u = v-(Ft/m) Equation 2

Given: F = 31  N, m = 11 kg, t = 4 s, v = 110 m/s

Substitute into equation 1

u = 110-(31×4/11)

u = 110-11.27

u = 98.73 m/s.

For, F = -10 N, v = 80 m/s

u = 80-(-10×4/11)

u = 80+3.63

u = 83.63 m/s

For, F = 47 N, v = 105 m/s

u = 105-(47×4/11)

u = 105-17.1

u = 87.9 m/s

The initial velocity at the the beginning of the time interval is 98.73 m/s, 83.63 m/s, 87.9 m/s

b would be the answer