In what two ways can a machine be made to be more efficient?

In which of the following situations has work been done? Select one: a. A weightlifter holds a 50kg barbell over his head for 3 minutes. b. A yoga instructor holds a handstand for 1 minute. c.

A rock group is playing in a bar. Sound emerging from the door spreads uniformly in all directions. The intensity level of the music is 116 dB at a distance of 2.82 m from the door.

A stone is thrown vertically upward with a speed of 12m/s from the edge of a cliff 70 m high (a) How much later it reaches the bottom of the cliff? (b) What is its speed just before hitting? And (c) what total distance did it travel? (Ans: 5.

A car is moving with a constant speed of 20 meters per second. What total distance does the car travel in 2 minutes

Julie drives 100 mi to Grandmother's house. on the way to grandmothers h's Julie drives half the distance at 40 mph and half the distance at 60 mph. On her return trip, she drives half the time at 40 mph and half the time at 60 mph.

A spring has a spring constant of 120 newtons per meter. Calculate the elastic potential energy stored in the spring when it is stretched 2.0 centimeters.

In pottery class, you throw a pot from a lump of wet clay. your pot's mass is 5.5 kg. after the pot is fired, it's mass is 4.9 kg. the density of wet clay is 1.60 g/cm3 and the density of fired clay is 1.36 g/cm3.

When you catch a baseball, what kind of work do you do, negative or positive? By catching the baseball, what do you change? Does the baseball gain or lose energy? What kind of energy?

A man finds that he has a mass of 100.6 kg. He goes on a diet, and several months later he finds that he has a mass of 96.4 kg. Express the mass 100.6 kg in scientific notation.

A bird has a kinetic energy of 3 J and a potential energy of 25 J. What is the mechanical energy of the bird?