Which of the following is an example of how a scientist might use a model
a- a stopwatch is used to time the rate of a chemical reaction
b- a microscope is used to magnify a group of cells
c- a wrench is used to tighten a nut onto a piece of wood
d- the end of a slinky is moved vertically up and down to stimulate a wave

Agroup of monkeys is trying to cross the river in a rowboat. the maximum buoyant force on the rowboat is 2,000 n. the weight of the rowboat is 1,000 n. each monkey has a weight of 150 n. how many monkeys can safely cross in the rowboat at one time? explain your reasoning, including any calculations you used to find the answer.