Which of the following laws best define this statement? the total amount of energy in a closed system stays the same.

An iron nail floats in mercury and sinks in water. Explain why?

At what stage of a reaction do atoms have the highest energy? a. reactant stage b. product stage c. transition state stage d. The stage of highest energy depends on the atom.

The loudness of a sound wave is affected by the wave's A. pitch B. frequency C. amplitude D. wavelength

Num determinado equipamento industrial, um líquido de calor específico 0,50 cal/g.°C, entra a 20 °C e sai a 80 °C. Se a vazão desse líquido no equipamento é de 50 kg/min, a potência térmica é, em kcal/min, de:

12. A boy of mass 50 kg running 5m/s jumps on to a 20kg trolley travelling in the same direction at 1.5m/s. Find their common velocity. Assume that there is no external unbalanced force working in the horizontal direction.

A wave has a wavelength of 50 m and a speed of 200 m/s. What is the frequency of this wave in hertz?

A 75.0 kg person stands on a scale in an elevator. (a) What does the scale read (in N and in kg) when the elevator is at rest?

Which of the following best describes the earth's average surface temperature for the past 900,000 years? A. a steady warming trend B. fairly steady temperatures until recently C. prolonged periods of cooling and warming D.

A capacitor with initial charge q0 is discharged through a resistor. What multiple of the time constant τ gives the time the capacitor takes to lose (a) the first 1/8-th of its charge (b) 7/8-th of its charge?

A sheet of paper has a mass of 5 grams. The paper is dropped from a high building twice (it reaches terminal speed in both cases), once as a flat paper of area 600 cm2 and once crumpled as a ball of radius 2 cm.