A truck starts from rest down a hill with a constant acceleration. It achieves 400 meters in 20 seconds. If the weight of the tru…

Question

A truck starts from rest down a hill with a constant acceleration. It achieves 400 meters in 20 seconds. If the weight of the truck is 7 tons then what will be the force acting on it?

1. A. 11000 Newtons
2. B. 12000 Newtons
3. C. 13000 Newtons
4. D. 14000 Newtons (Correct answer)

Correct Answer

Option D — 14000 Newtons

Detailed Solution & Explanation

The correct answer is 14000 Newtons.

Key Points

• This numerical is solved in two steps using the equations of motion and Newton's Second Law.
• Step 1 — find the acceleration. The truck starts from rest, so initial velocity u = 0.
• Using s = ut + (1/2)at² with s = 400 m and t = 20 s:
• 400 = 0 + (1/2) × a × (20)² = (1/2) × a × 400 = 200a, which gives a = 2 m/s².
• Step 2 — find the force. The mass of the truck is 7 tons = 7 × 1000 = 7000 kg.
• Applying F = ma:
• F = 7000 × 2 = 14000 N, which matches option (D).

Exam Tip

• the two habitual errors here are forgetting to convert tons to kilograms (1 metric ton = 1000 kg) and forgetting that u = 0 for a body starting from rest, which simplifies the equation to s = (1/2)at².
• Writing down the SI-unit conversion before substituting values eliminates both mistakes.

प्रश्न (हिन्दी में)

एक ट्रक विराम अवस्था से किसी पहाड़ी से नीचे की ओर नियत त्वरण से लुढ़कना शुरू करता है। यह 20 सेकेण्ड में 400 मीटर की दूरी तय करता है। यदि ट्रक का द्रव्यमान 7 टन है तो इस पर लगने वाला बल होगा:

1. A. 11000 न्यूटन
2. B. 12000 न्यूटन
3. C. 13000 न्यूटन
4. D. 14000 न्यूटन