Physics Answers

What is the wavelength in air under standard conditions of a compressional wave

whose frequency is 250 per second? Assume that the bulk modulus for air is 1.40

x 106 dyn/cm2 and the density of air is 1.29 g/L.

The velocity of light in a liquid is 0.80 as fast as it is in air. What is the index of

refraction of the liquid?

A tuning fork vibrates 200 times per second and sends out a compressional wave

that travels with a speed of 340 m/s. Find (a) the period and (b) the wavelength.

A steel rod 4 m long and 0.5 cm2

in cross sectional area is found to stretch 0.2

cm under a tension of 12000 N. Under these conditions, determine

(a) The stress

(b) The strain; and

(c) Young’s modulus for the material

A rigid plank 5.00 m long has mass 30.0 kg and supports a 75.0kg block 2.00 m from the left end. How much force is needed to support each end of the plank?

Find the tension in the horizontal part of the supporting cable, and the compression in the boom, elevated to 25.0°, of the crane that lifts a 8900.N load.

Suppose you have two capacitors 8.0 μF and 4.0 μF connected in series and parallel with points a and b whose potential

difference is 20 V. Find the equivalent capacitance and charge.

Suppose you have two capacitors 8.0 μF and 4.0 μF connected in series and parallel with points a and b whose potential

difference is 20 V. Find the equivalent capacitance and charge.

Example:

A steel railroad track has a length of 30.000 m when the temperature is 0°C. What is its length on

a hot day when the temperature is 40.0°C? (b) Suppose the track is nailed down so that it

can’t expand. What stress results in the track due to the temperature change

A 72.5 kg

k

g

 skater moving initially at 2.40 m/s

m

/

s

 on rough horizontal ice comes to rest uniformly in 3.52 s

s

 due to friction from the ice.

A, What force does friction exert on the skater?

Express your answer with the appropriate units. Enter positive value if the direction of the force is the same as that of the initial velocity of the skater and negative value if the direction of the force is opposite.