Question

part b - multiple choice

1. a 15 n force moves a box 4 m in the same direction.

how much work is done?
a) 3.75 j b) 11 j c) 45 j d) 60 j

1. a student performs 150 j of work in 3 seconds.

what is the students power output?
a) 25 w b) 50 w c) 75 w d) 450 w

1. a pendulum swinging back and forth best demonstrates:

a) chemical → electrical energy transformation
b) alternating potential and kinetic energy
c) loss of energy each swing
d) only kinetic energy being used

1. which situation demonstrates energy efficiency?

a) an engine that produces mostly heat instead of motion
b) a solar panel that converts 30% of sunlight into electricity
c) a light bulb that emits mostly heat instead of light
d) a toaster that glows red without heating bread

1. when you touch a metal spoon in hot soup, heat moves to your hand by:

a) conduction b) convection c) radiation d) evaporation

1. which of the following shows the correct order of energy transformations when

lighting a match?
a) thermal → chemical → radiant
b) mechanical → chemical → thermal + light
c) chemical → mechanical → nuclear
d) electrical → chemical → light

1. in photosynthesis, the energy transformation is:

a) light → chemical
b) chemical → mechanical
c) chemical → thermal
d) electrical → chemical

1. the energy stored in glucose molecules is used by organisms to make:

a) atp during cellular respiration
b) chlorophyll during photosynthesis
c) carbon dioxide during fermentation
d) light during bioluminescence

Explanation:

Step1: Work formula

Work \(W = F\times d\), where \(F = 15N\) and \(d=4m\).

Step2: Calculate work

\(W=15\times4 = 60J\).

Step3: Power formula

Power \(P=\frac{W}{t}\), where \(W = 150J\) and \(t = 3s\).

Step4: Calculate power

\(P=\frac{150}{3}=50W\).

Step5: Pendulum energy

A pendulum has alternating potential (at extreme positions) and kinetic (at mean position) energy.

Step6: Energy efficiency

A solar panel converting 30% of sunlight to electricity is more efficient than others (which waste energy as heat etc.).

Step7: Heat transfer

Heat transfer in metal (spoon) is by conduction.

Step8: Match energy transformation

Striking (mechanical) causes chemical reaction (in match head) to produce thermal and light.

Step9: Photosynthesis energy

Plants convert light (from sun) to chemical (glucose) in photosynthesis.

Step10: Glucose energy use

Organisms use glucose to make ATP in cellular respiration.

Answer:

1. d) 60 J
2. b) 50 W
3. b) Alternating potential and kinetic energy
4. b) A solar panel that converts 30% of sunlight into electricity
5. a) Conduction
6. b) Mechanical → Chemical → Thermal + Light
7. a) Light → Chemical
8. a) ATP during cellular respiration