Question 1

Which of the following is a necessary condition for an object to be in static equilibrium?

Accepted Answer

Both the net force and the net torque on the object must be zero.

Question 2

A uniform beam is supported at its ends and a heavy object is placed at its center. If the beam is in static equilibrium, which statement is true?

Accepted Answer

The sum of the upward forces at the supports equals the combined weight of the beam and the object.

Question 3

A ladder leans against a frictionless wall. Which pivot point would simplify the calculation of the torque due to the wall's force?

Accepted Answer

The point where the ladder contacts the wall.

Question 4

A car has a track width $$t$$ and a center-of-gravity height $$h. $$The critical angle for rollover is given by $$	an 	heta_c = t/(2h). If$$ $$h$$ increases while $$t$$ remains constant, what happens to $$	heta_c$$?

Accepted Answer

$$	heta_c$$ decreases

Question 5

A 61 kg woman stands on tiptoe. The upward force from the floor is 600 N at 0.15 m from the ankle pivot, and the Achilles tendon exerts an upward force at 0.05 m from the pivot. What is the tension in the tendon for static equilibrium?

Accepted Answer

1800 N

Question 6

Which of the following best describes the restoring force in a spring according to Hooke’s Law?

Accepted Answer

$$F_{sp} = -k \Delta x$$

Question 7

A steel rod of length $$L$$ and cross-sectional area $$A is $$stretched by a force $$F. $$The Young’s modulus $$Y$$ relates these quantities by which equation?

Accepted Answer

$$\frac{F}{A} = Y \frac{\Delta L}{L}$$

Question 8

A block is acted on by two equal and opposite forces, but the forces are not collinear. What is true about the block’s equilibrium?

Accepted Answer

The block has zero net force but nonzero net torque.

Question 9

Which material is most likely to return to its original shape after being stretched within the elastic limit?

Accepted Answer

Steel

Question 10

A rod is stretched beyond its elastic limit. What happens?

Accepted Answer

It becomes permanently deformed.

Question 11

A person stands with their toes against a wall and tries to rise onto their tiptoes. Why do they fall backward?

Accepted Answer

They cannot shift their center of gravity over their base of support.

Question 12

Which of the following increases the stability of an object?

Accepted Answer

Widening the base of support

Question 13

A spring with spring constant $$k is $$stretched by $$\Delta x. $$What is the potential energy stored in the spring?

Accepted Answer

$$U = \frac{1}{2} k (\Delta x)^2$

Question 14

Which of the following is a correct statement about the forces in the human ankle joint when standing on tiptoe?

Accepted Answer

The force in the Achilles tendon can be several times the person’s weight.

Question 15

A rod of length $$L$$ and area $$A is $$stretched by a force $$F$$ causing an extension $$\Delta L. $$What is the strain in the rod?

Accepted Answer

$$\frac{\Delta L}{L}$$

Question 16

Which of the following best describes the difference between rigid and pliant materials?

Accepted Answer

Rigid materials experience small deformations under normal forces.

Question 17

A massless rod is supported at one end and a 1000 N weight is hung at the other. A scale is placed halfway between the support and the weight. What does the scale read?

Accepted Answer

500 N

Question 18

Which of the following is true about the torque due to a force acting at a pivot point?

Accepted Answer

It is zero at the pivot point.

Question 19

A biological material has a high Young’s modulus. What does this imply?

Accepted Answer

It is very rigid.

Equilibrium and Elasticity: Static Equilibrium, Stability, and Elastic Properties of Materials

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