11.

A car moves from A to B with a speed of 30 km/h and from B to A with a speed of 20 km/h. What is the average speed of the car ?

• 25 km/h

• 24 km/h

• 50 km/h

• 10 km/h

A body starts from rest and moves with constant acceleration for t sec. It travels a distance x₁ in first half of time and x₂ in next half of time, then

• x₂ = x₁

• x₂ = 2x₁

• x₂ = 3x₁

• x₂ = 4x₁

What is the source temperature ofthe Carnot engine required to get 70% efficiency ? Given, sink temperature = 27°C.

• 1000°C

• 90°C

• 270°C

• 727°C

A 10 kg metal block is attached to a spring of spring constant 1000 Nm^-1. A block is displaced from equilibrium position by 10 cm and released. The maximum acceleration of the block is

• 10 ms^-2

• 100 ms^-2

• 200 ms^-2

• 0.1 ms^-2

A metallic wire of 1 m length has a mass of 10 x 10^-3 kg. If a tension of 100 N is applied to a wire, what is the speed of transverse wave ?

• 100 ms^-1

• 10 ms^-1

• 200 ms^-1

• 0.1 ms^-1

A trainis approaching towards a platform with a speed of 10 ms^-1 while blowing a whistle of frequency 340 Hz. What is the frequency of whistle heard by a stationary observer on the platform ? Given speed of sound = 340 ms^-1.

• 330 Hz

• 350 Hz

• 340 Hz

• 360 Hz

A flow of liquid is streamline, if the Reynold's number is

• less than 1000

• greater than 1000

• between 2000 to 3000

• between 4000 to 5000

A pipe of 30 cm long and open at both the ends produces harmonics. Which harmonic mode of pipe resonates a 1.1 kHz source? Given, speed of sound in air = 330 ms^-1.

• Fifth harmonic

• Fourth harmonic

• Third harmonic

• Second harmonic

In anomalous expansion of water, at what temperature, the density of water is maximum ?

• 4°C

• < 4°C

• > 4°C

• 10°C

A cycle tyre bursts suddenly. What is the type of this process ?

• Isothermal 

• Adiabatic

• Isochoric

• Isobaric