A Styrofoam box has a surface area of 0.20 m^2 and a wall thickness of 2.0 cm. The temperature of the inner surface is 0°C, and the outside temperature is 25°C. If it takes 2.0 hr for 5.0 kg of Si wafers to increase temperature from the initial 0°C to 10°C, determine the thermal conductivity of the Styrofoam. The molar heat capacity of bulk Si is 19.8 J/mol. K, molar mass of Si is 28.0 g/mol. Required:
Determine the thermal conductivity of the Styrofaom.

An object weighs 40n in air, weighs 20n when submerged in water and 30n when submerged in a liquid of unknown density. what is the density of the liquid?

The frequency of vibrations of a vibrating violin string is given by f = 1 2l t ρ where l is the length of the string, t is its tension, and ρ is its linear density.† (a) find the rate of change of the frequency with respect to the following. (i) the length (when t and ρ are constant) (ii) the tension (when l and ρ are constant) (iii) the linear density (when l and t are constant) (b) the pitch of a note (how high or low the note sounds) is determined by the frequency f. (the higher the frequency, the higher the pitch.) use the signs of the derivatives in part (a) to determine what happens to the pitch of a note for the following. (i) when the effective length of a string is decreased by placing a finger on the string so a shorter portion of the string vibrates df dl 0 and l is ⇒ f is ⇒ (ii) when the tension is increased by turning a tuning peg df dt 0 and t is ⇒ f is ⇒ (iii) when the linear density is increased by switching to another string df dρ 0 and ρ is ⇒ f is ⇒

Imagine that someone pushes one marble toward a motionless marble. would there still be action-reaction forces involved in the collision? how might the marbles’ motions be changed? ?