OAR OAR Mechanical Comprehension: Forces 2

Question 1

A 10 kg box is pushed across a frictionless surface with a net force of 30 N. What is the box's acceleration?

Accepted Answer

3 m/s²

Answer

Newton's second law: a = F/m = 30/10 = 3 m/s².

Question 2

Two forces act on an object: 15 N to the right and 9 N to the left. What is the magnitude and direction of the net force?

Accepted Answer

6 N to the right

Answer

Net force = 15 − 9 = 6 N in the direction of the larger force (right).

Question 3

Which of the following best describes a force couple?

Accepted Answer

Two equal and opposite forces that produce rotation

Answer

A couple consists of two equal, opposite, non-collinear forces that produce pure rotation (torque) with no net linear force.

Question 4

An object is in static equilibrium. Which statement must be true?

Accepted Answer

The net force and net torque on it are both zero

Answer

Static equilibrium requires both the sum of all forces and the sum of all torques to equal zero.

Question 5

A 500 N person stands on a scale in an elevator accelerating upward at 2 m/s². What does the scale read? (g ≈ 10 m/s²)

Accepted Answer

600 N

Answer

Mass = 50 kg; scale reads N = m(g + a) = 50(10 + 2) = 600 N.

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