A ball of mass 1 kg and another of mass 2 kg are dropped from a tall building whose height is 80 m. After, a fall of 40 m each towards Earth, their respective kinetic energies will be in the ratio of

(a)

\(\sqrt2:1\)

(b)

\(1:\sqrt2\)

(c)

2:1

(d)

1:2

A particle of mass m is being rotated on a vertical circle of radius r. If the speed of particle at the highest point be v, then ______________.

(a)

mg=\(\frac{mv^{2}}{r}\)

(b)

mg>\(\frac{mv^{2}}{r}\)

(c)

mg<\(\frac{mv^{2}}{r}\)

(d)

mg≥\(\frac{mv^{2}}{r}\)

The coefficient of restitution e for a perfectly elastic collision is ______________.

(a)

1

(b)

0

(c)

\(\alpha\)

(d)

-1

The potential energy of a system increases, if work is done

(a)

by the system against a conservative force

(b)

by the system against a non-conservative force

(c)

upon the system by a conservative force

(d)

upon the system by a non- conservative force

The work done by the conservative force for a closed path is

(a)

always negative

(b)

zero

(c)

always positive

(d)

not defined

Two equal masses m₁ and m₂ are moving along the same straight line with velocities 5ms^-1 and -9 ms^-1 respectively. If the collision is elastic, then calculate the velocities after the collision of m₁ and m₂ respectively

(a)

-4 ms^-1 and 10 ms^-1

(b)

10 ms^-1 and 0 ms^-1

(c)

-9 ms^-1 and 5 ms^-1

(d)

5 ms^-1 and 1 ms^-1

A cricket ball falls from a height of 40 m. What is the velocity with which the ball hits the ground?

(a)

40 m/s

(b)

20 m/s

(c)

16 m/s

(d)

28 m/s

Convert 1 kwh in joule ______________.

(a)

1.2\(\times\)10² J

(b)

2.4\(\times\)10⁴ J

(c)

3.6 \(\times\)10⁶ J

(d)

4.4 \(\times\)10³ J

An engine pumps water continuously through a hose. Water leaves the hose with a velocity v and m is the mass per unit length of the water of the jet. What is the rate at which kinetic energy is imparted to water?

(a)

\({{1}\over{2}}{m}{v}^{2}\)

(b)

mv³

(c)

\({{1}\over{2}}{m}{v}^{3}\)

(d)

\({{1}\over{2}}{m}{v}^{2}\)

Two equal masses m₁ and m₂ moving along the same straight line with velocities +3 m/s and -5 m/s respectively collide elastically. Their velocities after the collision will be respectively _______________.

(a)

- 4 m/s and +4 m/s

(b)

+4 m/s for both

(c)

- 3 m/s and +5 m/s

(d)

- 5 m/s and + 3 m/s