1
JEE Main 2021 (Online) 31st August Evening Shift
Numerical
+4
-1
The diameter of a spherical bob is measured using a vernier callipers. 9 divisions of the main scale, in the vernier callipers, are equal to 10 divisions of vernier scale. One main scale division is 1 mm. The main scale reading is 10 mm and 8th division of vernier scale was found to coincide exactly with one of the main scale division. If the given vernier callipers has positive zero error of 0.04 cm, then the radius of the bob is ___________ $$\times$$ 10$$-$$2 cm.
2
JEE Main 2021 (Online) 26th August Evening Shift
Numerical
+4
-1
The acceleration due to gravity is found upto an accuracy of 4% on a planet. The energy supplied to a simple pendulum to known mass 'm' to undertake oscillations of time period T is being estimated. If time period is measured to an accuracy of 3%, the accuracy to which E is known as ..............%
3
JEE Main 2021 (Online) 25th July Morning Shift
Numerical
+4
-1
Student A and student B used two screw gauges of equal pitch and 100 equal circular divisions to measure the radius of a given wire. The actual value of the radius of the wire is 0.322 cm. The absolute value of the difference between the final circular scale readings observed by the students A and B is ______________.

[Figure shows position of reference 'O' when jaws of screw gauge are closed]

Given pitch = 0.1 cm.

4
JEE Main 2021 (Online) 22th July Evening Shift
Numerical
+4
-1
Three students S1, S2 and S3 perform an experiment for determining the acceleration due to gravity (g) using a simple pendulum. They use different lengths of pendulum and record time for different number of oscillations. The observations are as shown in the table.

Student
No.
Length of
Pendulum (cm)
No. of
oscillations (n)
Total time for
n oscillations
Time
period (s)
1 64.0 8 128.0 16.0
2 64.0 4 64.0 16.0
3 20.0 4 36.0 9.0

(Least count of length = 0.1 cm and Least count for time = 0.1 s)

If E1, E2 and E3 are the percentage errors in 'g' for students 1, 2 and 3 respectively, then the minimum percentage error is obtained by student no. ______________.