Theo was doing research to support the claim that exercise increases heart and lung health. he had 50 people do a rigorous exercise program. each week, for six months, he tested their heart and respiratory rate. he determined that exercise does increase heart and lung health. which best describes his claim? a. it is valid because he used multiple trials. b. it is invalid because he did not have a control group. c. it is invalid because his sample size was small. d. it is valid because he controlled the exercise program.

During spring semester at mit, residents of the parallel buildings of the east campus dorms battle one another with large catapults that are made with surgical hose mounted on a window frame. a balloon filled with dyed water is placed in a pouch attached to the hose, which is then stretched through the width of the room. assume that the stretching of the hose obeys hooke's law with a spring constant of 89.0 n/m. if the hose is stretched by 5.80 m and then released, how much work does the force from the hose do on the balloon in the pouch by the time the hose reaches its relaxed length? unitst 3 number-1497 the tolerance is +/-5% open show work click if you would like to show work for this question:

Avoltaic cell converts chemical energy to

Why does a collision with an airbag cause less damage than a collision with a steering wheel