Laws of Motion Test

Result

Laws of Motion Test - 12

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Weekly Quiz Competition

Question 1
1 / -0

A stone of mass 0.25 kg tied to the end of a string is whirled round in a circle of radius 1.5 m with a speed of 40 rev./min in a horizontal plane. The speed is then increased beyond the maximum permissible value, and the string breaks suddenly, which of the following correctly describes the trajectory of the stone after the string breaks

A
the stone moves radially inwards

B
the stone flies off at an angle with the tangent whose magnitude depends on the speed of the particle.

C
the stone flies off tangentially from the instant the string breaks

D
the stone moves radially outwards

Solution

it is because the velocity at any point is directed along the tangent at that point.
Question 2
1 / -0

A helicopter of mass 1000 kg rises with a vertical acceleration of 15 m s⁻² . The crew and the passengers weigh 300 kg. Give the magnitude and direction of the force on the helicopter due to the surrounding air.

A
3.95 × 10⁴ N upwards

B
3.70 × 10⁴ N upwards

C
3.25 × 10⁴ N upwards

D
3.50 × 10⁴ N downwards

Solution

Force on the helicopter due to the surrounding air is equal and opposite to the action of the rotor of the helicopter on the surrounding air.

therefore Force on the surrounding air is (1000+300)(10+15) = 32500 N in upward direction