Question

question 8 (1 point)
a cheerleader is thrown vertically upward into the air. as the cheerleader rises, which one of the following quantities increases?
a. gravitational potential energy d. acceleration
b. speed e. mechanical energy
c. kinetic energy

a

b

c

d

e
question 9 (1 point)
a boy decides to ignite caps from a toy gun in the following manner: he uses a magnifying glass to focus the suns rays on a cap. it ignites with a loud bang. which of the following energy transformations best describes the situation?
a. sound → chemical → radiant d.sound → radiant → chemical
b. radiant → chemical → sound e.none of the above
c. chemical → radiant → sound

a

Explanation:

Question 8

• Option a: Gravitational potential energy ($U = mgh$) depends on height ($h$). As the cheerleader rises, $h$ increases, so $U$ increases.
• Option b: When moving upward against gravity, speed decreases (decelerated by gravity).
• Option c: Kinetic energy ($K=\frac{1}{2}mv^2$) depends on speed ($v$). Since speed decreases, kinetic energy decreases.
• Option d: Acceleration is due to gravity ($g$), which is constant near the Earth's surface, so acceleration doesn't increase.
• Option e: Mechanical energy (sum of kinetic and potential) is conserved (ignoring air resistance), so it doesn't increase.

• The sun's rays are radiant energy. This radiant energy is used to ignite the cap (chemical energy in the cap is released/transformed). Then, the ignition produces a bang (sound energy). So the energy transformation is radiant (sun) → chemical (in cap) → sound (bang).
• Option a: Incorrect order (starts with sound).
• Option c: Starts with chemical, but the initial energy is from the sun (radiant).
• Option d: Incorrect order.
• Option e: Incorrect, as option b is correct.

Answer:

a. gravitational potential energy

Question 9