Here are the expected answers for the activity's guiding questions.
Question 1: How does the angle of the applied force affect the work done?
Answer: As the angle ( \theta ) increases from 0° to 90°, the work done decreases. This is because the component of the force that acts in the direction of displacement (( F \cos \theta )) becomes smaller. At 90°, the force is perpendicular to the displacement, so no work is done (the object moves sideways but not away from the force).
Question 2: State the condition where maximum work is done.
Answer: Maximum work is done when the force is applied in the same direction as the displacement (( \theta = 0^\circ )). In this case, ( \cos 0^\circ = 1 ), so ( W = F \times s ).
Question 3: State the condition where no work is done, even though a force is applied. Here are the expected answers for the activity's
Answer: No work is done in the following situations:
Question 4: Why is the spring balance reading not exactly the same for each angle? (Real experiment)
Answer: When the string is pulled at an angle, the vertical component of the pulling force (( F \sin \theta )) reduces the normal force (( R )) of the block on the surface. Since friction (( f )) is proportional to normal force (( f = \mu R )), friction decreases as angle increases. To maintain constant velocity (if required), the spring balance reading may actually change. However, if the question asks purely about theoretical work, we ignore friction.
Berdasarkan pengalaman peperiksaan, berikut adalah 3 kesilapan paling lazim:
Lupa Menukar Unit
Mengabaikan Arah Daya (Mengabaikan cos θ)
Tip Peperiksaan: Selalu lukis gambar rajah jasad bebas (free body diagram) dan tentukan arah sesaran. Jika daya tidak selari, cari komponen daya yang selari dengan sesaran.
Berikut adalah simulasi jawapan yang dijangkakan berdasarkan dapatan eksperimen biasa dan soalan formatif yang berkaitan. Saya akan menyusunnya dalam format "Soalan & Jawapan".
If you push a box with a force of 20 N for 5 meters, the work done would be:
[ W = 20 , \textN \times 5 , \textm = 100 , \textJ ] Question 4: Why is the spring balance reading
For work to be done, two conditions must be met:
Aktiviti ini biasanya melibatkan jadual perbandingan situasi untuk menentukan sama ada kerja dilakukan atau tidak.
Soalan: Sebuah kotak dikenakan daya 20 N dan bergerak pada jarak 5 m di atas lantai licin. Berapakah kerja yang dilakukan?
Jawapan: $$W = F \times s$$ $$W = 20 , \textN \times 5 , \textm$$ $$W = 100 , \textJ$$
W = F · s · cosθ