Mechanics | Relativity Answers

A second year physical sciences student drives at an average speed of 40 km/h to see a friend, 

who lives a distance of 100km/h away (you may take the problem as being one-dimensional!). 

On arrival she discovers that he has misunderstood the arrangements and has already left to 

drive to visit her. She returns home, driving at an average speed of 70 km/h on the return trip. 

What is her average velocity for the whole journey? What is her average speed? If each left 

originally at the same time and his average speed is 30 km/h, who arrives first at her house? 

What happens to the mass of water in a

pot when it cools, assuming no

molecules escape or are added? Is this

observable in practice? Explain.

Consider a mixture of 2 mol of helium and 4 mol of oxygen. Compute the speed of sound in this gas mixture at 300 K

Two electric train A and B leave the same station on parallel rail line train A start at rest with a uniform acceleration of 0.2m/s2 and attain a speed of 45km/h and maintain this speed at constant rate after ward . the train B leave the station 1 minute after train A has left and move with uniform acceleration of 0.4m/s2 to attain a maximum speed of 72 km/h. If train B maintain the speed of 72km/h determine the time it will over take train A

A source passing a stationary observer is emitting a frequency of 560 Hz. If the speed of sound is 345 m/s, what must the speed of the source be if the frequency of the source is 480 Hz? (Ans: 58 m/s)

You are moving in a car at 90 km/h and you see someone at the side of the highway. You can use your horn to warn the person. The frequency of the horn is 440 Hz. and the air temperature is 0°C. Calculate the frequency of the horn the person hears as you approach and pass. (Ans: Approaching: 480 Hz, Passing: 409 Hz)

A fire truck is emitting a 450 Hz signal passes by a stationary detector. The difference in frequency measured by the detector is 58 Hz. If the speed of sound is 345 m/s, how fast is the truck moving? (ans: 22m/s)

A spring is hung from the ceiling. When a 0.450-kg block is attached to the free end of the spring and released from rest, the block drops 5.0 cm before momentarily coming to rest, after which it moves back upward. What is the spring constant of the spring?

An object is being shot from a horizontal ground at an incline angle of 30 degree with respect to the ground at a speed of 49 m/s. Find the duration in seconds that the object is above the height of 13 m. Give your answer with one decimal place.

The difference between the ice point and steam point in a liquid in glass thermometer is 30cm. What temperature is recorded when the mercury thread is 10cm above the ice point?