Question

What is the size of the net force needed to stop a 82.1 g mass moving 9.5 m/s in 5. seconds? (Give the absolute value of the answer in newtons)

Answer 1

Mass of the object = m = 82.1 g = 82.1 x 10^-3 kg

Initial velocity of the object = V₁ = 9.5 m/s

Final velocity of the object = V₂ = 0 m/s (The object is stopped)

Time period in which the object is stopped = T = 5 sec

Acceleration of the object = a

V₂ = V₁ + aT

0 = 9.5 + a(5)

a = -1.9 m/s²

Negative as it is deceleration.

Net force on the object = F_net

F_net = ma

F_net = (82.1x10^-3)(-1.9)

F_net = -0.156 N

The negative sign indicates the force is acting in the opposite direction of the motion of the object.

We are asked for the absolute value therefore the final answer will be positive.

Net force needed to stop a 82.1 g mass moving at 9.5 m/s in 5 sec = 0.156 N