Question
A train approaches a stationary observer with a speed of
36 km/h. It emits a sound of frequency 500 Hz. If the speed of sound is 340 m/s, what is the apparent frequency heard by the observer?Solution
The apparent frequency (f′) heard by a stationary observer when a source is moving towards them is given by the Doppler effect formula: 
Raj, Sanjay and Vaibhav can separately finish a work in 20, 30 and 40 days, respectively. In how many days Raj can finish the work if he is assisted.by ...
- Person A is twice as efficient as Person B. Person B can complete a certain task in 32 days, while Person C takes 4 days more than Person A to finish the s...
- Ayaan and Kabir started working together on a task. Ayaan does 4 units per day and Kabir can finish the full task in 25 days alone. The total work is 100 u...
A red JCB machine can complete the excavation of a field in 10 days, while a green JCB machine can accomplish the same task in 15 days. If both machines...
Working together, Amit and Pawan can finish a task in 22.5 days, and Pawan and Chirag can complete 60% of the same task in 14.4 days. Given that Amit is...
A and B can complete a job together in 30 days; B and C can complete the same job together in 25 days, while C and A can complete the same job together ...
Karan, Arjun and Krunal alone can complete a work in 40, 60 and 48 days respectively. All of them started working together but after 3 days from start K...
‘M’ alone can complete a work in 18 days. ‘N’ is 50% as efficient as ‘M’. How long will they take to complete the work together?
...‘A’ can do a piece of work in 10 days. ‘B’ can do 70% of the same work in 20 days. If they work together for the entire time and get paid Rs.108...
Ajay and Vijay can finish a task in 9 days working together. Charu, who is twice as efficient as Vijay, can complete the task alone in 18 days. If Ajay ...
Relevant for Exams:
