An aircraft executes a horizontal loop of radius 1.00 km with a steady speed of 900 km/h. Then the ratio of its centripetal acceleration with the acceleration due to gravity is:

1. 5.4:1
2. 6.4:1
3. 4:1
4. 1:1

A stone tied to the end of a string 80 cm long is whirled in a horizontal circle at a constant speed. If the stone makes 14 revolutions in 25 sec, what is the magnitude of the acceleration of the stone?
1. 8.1 ms^-2
2. 7.7 ms^-2
3. 8.7 ms^-2
4. 9.9 ms^-2

Which one of the following is not true?

A cyclist is riding at a speed of 27 km/h. As he approaches a circular turn on the road of a radius of 80 m, he applies brakes and reduces his speed at a constant rate of 0.50 m/s every second. What is the magnitude of the initial acceleration of the cyclist on the circular turn?

1. 0.66 ${\mathrm{ms}}^{-2}$

2. 0.56 ${\mathrm{ms}}^{-2}$

3. 0.86 ${\mathrm{ms}}^{-2}$

4. 0.16 ${\mathrm{ms}}^{-2}$