Question

A man pushed the box with a force of 20 N. The mass of the box doubled, but he still pushed with a force of 20 N.

Which option describes how the acceleration of the box after the mass was doubled?

a) The acceleration is 2x the original acceleration

b) Acceleration is 4x the original acceleration

c) Acceleration is 1/2x the original acceleration

d) Acceleration is 1/4x the original acceleration

Answer 1

Option (c) Acceleration is 1/2x the original acceleration

Step-by-step explanation:

To know the the correct answer to the question, we shall determine the acceleration of the box in each case.

Case 1:

Mass (m) = m

Force (F) = 20 N

Acceleration 1 (a₁) =?

F = ma₁

20 = m × a₁

Divide both side by m

a₁ = 20 / m

Case 2:

Mass (m) = 2m

Force (F) = 20 N

Acceleration 2 (a₂) =?

F = ma₂

20 = 2m × a₂

Divide both side by 2m

a₂ = 20 / 2m

a₂ = 10 / m

Finally, we shall determine the acceleration of the box after the mass was doubled. This can be obtained as illustrated below:

Acceleration 1 (a₁) = 20 / m

Acceleration 2 (a₂) = 10 / m

a₂ : a₁ = 10 / m : 20 / m

a₂ / a₁ = 10 / m ÷ 20 / m

a₂ / a₁ = (10 / m) × (m / 20)

a₂ / a₁ = ½

Cross multiply

a₂ = ½a₁

Thus, the acceleration of the box after the mass was doubled is ½ times the original acceleration.