JEE Mains · Physics · STD 11 - 2. motion in straight line
A train starting from rest first accelerates uniformly up to a speed of \(80 \mathrm{~km} / \mathrm{h}\) for time \(t\), then it moves with a constant speed for time 3t. The average speed of the train for this duration of journey will be (in \(\mathrm{km} / \mathrm{h}\) ) _______.
- A \(80\)
- B \(70\)
- C \(30\)
- D \(40\)
Answer & Solution
Correct Answer
(B) \(70\)
Step-by-step Solution
Detailed explanation
Given: Final speed = \(80 \, \text{km/h}\) Time of acceleration = \(t\) Time at constant speed = \(3t\) Solution: During uniform acceleration from rest, \(\text{Average speed} = \frac{0 + 80}{2} = 40 \, \text{km/h}\) Distance covered during acceleration: \(s_1 = 40t\) Distance…
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