Rotational Equilibrium and Newton's First Law in Rotational Form AP Physics 1 MCQ

Rotational Equilibrium and Newton’s First Law in Rotational Form AP Physics 1 MCQ – Exam Style Questions etc.

Rotational Equilibrium and Newton’s First Law in Rotational Form AP Physics 1 MCQ

Unit 5: Torque and Rotational Dynamics

Weightage : 10-15%

AP Physics 1 Exam Style Questions – All Topics

Question

A 5-meter uniform plank of mass 100 kilograms rests on the top of a building with 2 meters extended over the edge as shown. How far can a 50-kilogram person venture past the edge of the building on the plank before the plank just begins to tip?
(A) 0.5 m (B) 1 m (C) 1.5 m ( D) 2 m

Answer/Explanation

Ans:B

Solution: Apply rotational equilibrium using the corner of the building as the pivot point. Weight of plank (acting at midpoint) provides torque on left and weight of man provides torque on right.
(m₁g) • r₁ = (m₂g) • r₂
(100 kg) (0.5m) = (50 kg) (r) → r = 1m

Question

A rod on a horizontal tabletop is pivoted at one end and is free to rotate without friction about a vertical axis, as shown. A force F is applied at the other end, at an angle θ to the rod. If F were to be applied perpendicular to the rod, at what distance from the axis should it be applied in order to produce the same torque?

(A) L sin θ (B) L cos θ (C) L (D) L tan θ

Answer/Explanation

Ans:A

Solution: Finding the torque in the current configuration we have:
(Fsinθ)(L) = FL sin θ.
To get the same torque with F applied perpendicular we would have to change the L to get F (Lsinθ)

Rotational Equilibrium and Newton’s First Law in Rotational Form AP Physics 1 MCQ