A scientist claims that a certain chemical will make fabric waterproof. Which option describes a controlled experiment that will produce evidence that will
support or refute her claim?
A. Two groups of fabric are treated with the chemical. One group is
cotton and the other is polyester. Then each group is exposed to
water.
B. One group of fabric is treated with the chemical, and the other
group is not. Then each group is exposed to water.
C. One group of fabric is treated with a small amount of the
chemical, and the other group is treated with a large amount. Then
each group is exposed to water.
O D. Two groups of fabric are treated with the chemical. Then one
group is exposed to a small amount of water, and the other group
is exposed to a large amount.

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.

the ima (higher than 1m) will be greater than the ima with the height of 1m.