Choose the letter that best answers the question or completes the statement.

1. In a controlled experiment,

   1. there are multiple responding variables.

   2. the responding variable is kept constant.

   3. the manipulated variable is kept constant.

   4. the responding variable is deliberately changed.

   5. only one variable at a time is deliberately changed.

2. The speed of an object indicates how far it travels in a given amount of time. If an electron travels $2.42 \times {10}^8$ meters in 2.00 seconds, what is the speed of this electron in cm/s?

   1. $1.21 \times {10}^8 \mathrm{cm}/\mathrm{s}$

   2. $4.84 \times {10}^8 \mathrm{cm}/\mathrm{s}$

   3. $1.21 \times {10}^{10} \mathrm{cm}/\mathrm{s}$

   4. $2.42 \times {10}^{10} \mathrm{cm}/\mathrm{s}$

   5. $4.84 \times {10}^{10 }\mathrm{cm}/\mathrm{s}$

3. A doctor measures the temperature of a patient to be 101°F. What is this temperature in kelvins?

   1. 38.3 K

   2. 73.8 K

   3. 214 K

   4. 311 K

   5. 346 K

4. The density of seawater is $1.024 \times {10}^3 \mathrm{kg}/{\mathrm{m}}^3$. What is the density of seawater in g/cm³?

   1. 102.4 g/cm³

   2. $1.024 \times {10}^{-6} \mathrm{g}/{\mathrm{cm}}^3$

   3. $1.024 \times {10}^3 \mathrm{kg}/{\mathrm{m}}^3$

   4. $3.072 \times {10}^3 \mathrm{g}/{\mathrm{cm}}^3$

   5. $1.024 \times {10}^9 \mathrm{g}/{\mathrm{cm}}^3$

5. A student conducts an experiment by dropping a basketball and a box of cereal of the same weight from the top of a building. The student measures the time it takes for each object to strike the ground. What was the student's hypothesis?

   

   1. A basketball weighs more than cereal.

   2. Curved objects travel through the air faster than flat objects.

   3. Heavier objects travel through the air faster than lighter objects.

   4. Gravity pulls on objects of the same weight with the same force.

   5. Heavier objects strike the ground with a greater force than lighter objects.

6. If two variables are directly proportional, then

   1. an increase in one variable causes a decrease in the other variable.

   2. the product of the two variables is constant.

   3. the ratio of the two variables is constant.

   4. neither variable is the controlled variable.

   5. both variables are constant.

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