The work done in moving an alpha particle between two points having potential difference 25 V is

• 8 × 10^-18 J

• 8 × 10^-19 J

• 8 × 10^-20 J

• 8 × 10^-16 J

The physical quantity angular momentum has the same dimensions as that of

• work

• force

• Planck's constant

• torque

The values of two resistors are R₁ = (6 ± 0.3)kΩ and R₂ = (10 ± 0.2)kΩ. The percentage error in the equivalent resistance when they are connected in parallel is

• 5.125 %

• 2 %

• 10.125 %

• 7 %

Two trains are moving with equal speed in opposite directions along two parallel railway tracks. If the wind is blowing with speed u along the track so that the relative velocities of the trains with respect to the wind are in the ratio 1 : 2, then the speed of each train must be

• 3u

• 2u

• 5u

• 4u

Two balls are dropped to the ground from different heights. One ball is dropped 2 s after the other but they both strike the ground at the same time. If the first ball takes 5 s to reach the ground, then the difference in initial heights is (g = 10 ms^-2)

• 20 m

• 80 m

• 170 m

• 40 m

A ball is thrown vertically upwards with a velocity of 25 ms^-1 from the top of a tower of height 30 m. How long will it travel before it hits ground ?

• 6 s

• 5 s

• 4 s

• 12 s

A ball is projected from the ground at a speed of 10 ms^-1 making an angle of 30° with the horizontal. Another ball is simultaneously released from a point on the vertical line along the maximum height of the projectile. The initial height of the second ball is (g = 10 ms^-2)

• 6.25 m

• 2.5 m

• 1.25 m

• 5 m

8.

The sum of the magnitudes of two forces acting at a point is 18 N and the magnitude of their resultant is 12 N. If the resultant is at 90° with the smaller force, the magnitude of the forces in N are

• 6, 12

• 11, 7

• 5, 13

• 14, 4

The position of a particle is given by $\mathrm{r} = \hat{\mathrm{i}} + 2\hat{\mathrm{j}} - \hat{\mathrm{k}}$ and its linear momentum is given by $\mathrm{p} = 3\hat{\mathrm{i}} + 4\hat{\mathrm{j}} - 2\hat{\mathrm{k}}$. Then its angular momentum, about the origin is perpendicular to

• yz-plane

• z-axis

• y-axis

• x-axis

A mass of 6 kg is suspended by a rope of length 2 m from a ceiling. A force of 50 N in the horizontal direction is applied at the mid-point of the rope. The angle made by the rope with the vertical, in equilibrium is

• 50°

• 60°

• 30°

• 40°