Question

A 0.12-kg apple falls off a tree branch that is 2.3 m above the thick grass. The apple sinks 0.067 m into the grass while stopping. Determine the average contact force that the grass alone exerts on the apple while stopping it. Ignore air resistance.

Answer 1

F = 20 N

Step-by-step explanation:

Given:

m = 0.12 kg

H = 2.3 m

S = 0.067 m

g = 9.8 m/s²

____________

F - ?

1)

Potential energy over grass:

Wp = m*g*H = 0.12*9.8*2.3 ≈ 2.7 J

2)

Work against the friction force of the grass:

A = F₁*S

3)

According to the law of conservation of energy:

A = Wp

F₁*S = Wp

F₁ = Wp / S = 2.7 / 0.067 ≈ 40 N

4)

Average grass resistance strength:

F = F₁ / 2 = 40 / 2 = 20 N