Question
A metal wire has length 5.2 m and diameter 1.0 mm. The metal has Young modulus 360 GPa. The wire is fixed at one end and a force is applied to the other end. The force extends the wire by 7.2 mm. The wire obeys Hooke’s law.
What is the force applied to the wire?
(A) $1.2 × 10^{2}N$
(B) $3.9 × 10^{2}N$
(C) $5.0 × 10^{2}N$
(D) $1.6 × 10^{3}N$
Answer/Explanation
Ans: B
Question
What is meant by the spring constant of a spring?
(A) extension per unit force
(B) $ \frac{1}{2}\times force × extension$
(C) force × extension
(D) force per unit extension
▶️Answer/Explanation
Ans: D
Question
A lamp is suspended in equilibrium from a fixed support by three long identical wires.
The weight of the lamp causes each wire to have an extension of 0.40 cm. The height h of the lamp above the floor is measured. The middle wire suddenly breaks
and the lamp falls a small distance as the extensions of the remaining two wires increase. The wires obey Hooke’s law. When the lamp is in equilibrium, the height h of the lamp above the floor is measured again.
What is the difference between the two values of h?
(A) 0.20 cm
(B) 0.27 cm
(C) 0.40 cm
(D) 0.60 cm
▶️Answer/Explanation
Ans: A
Question
An object of mass m is suspended by a spring from a fixed point.
The spring has spring constant k. The object is set into vertical oscillations of period T. Which equation for T is homogeneous with respect to base units?
A \(T=2\pi (\frac{k}{m})\)
B \(T=2\pi (\frac{m}{k})\)
C \(T=2\pi \sqrt{\frac{k}{m}}\)
D \(T=2\pi \sqrt{\frac{m}{k}}\)
▶️Answer/Explanation
Ans D