In the arrangement shown in the figure, the ends P and Q of an inextensible string move downwards with uniform speed u. Pulleys A and B are fixed. The mass M moves upwards with a speed

1. \(2u~cos\theta\)

2. \(u/cos\theta\)

3. \(2u/cos\theta\)

4. \(ucos\theta\)

When Neils Bohr shook hand with Werner Heisenberg, what kind of force they exerted?
1. Gravitational
2. Electromagnetic
3. Nuclear
4. Weak

Let E, G and N represent the magnitudes of electromagnetic, gravitational and nuclear forces between two electrons at a given separation. Then

1. N > E > G

2. E > N > G

3. G > N > E

4. E > G > N

The sum of all electromagnetic forces between different particles of a system of charged particles is zero

1. only if all the particles are positively charged

2. only if all the particles are negatively charged

3. only if half the particles are positively charged am half are negatively charged

4. irrespective of the signs of the charges

A \(60\) kg man pushes a \(40\) kg man by a force of \(60\) N. The \(40\) kg man has pushed the other man with a force of:
1. \(40\) N
2. \(0\)
3. \(60\) N
4. \(20\) N

A neutron exerts a force on a proton which is

(a) gravitational

(b) electromagnetic

(c) nuclear

(d) weak

Choose the correct option:

1. (a) and (b)

2. (a) and (c)

3. (b) and (c)

4. (a) and (d)

A proton exerts a force on a proton which is

(a) gravitational

(b) electromagnetic

(c) nuclear

(d) weak

Choose the correct option:

1. (a), (b) and (c)

2. (b), (c) and (d)

3. (a) and (b)

4. (b) and (c)

Mark the correct statements :

(a) The nuclear force between two protons is always greater than the electromagnetic force between them

(b) The electromagnetic force between two protons is always greater than the gravitational force between them

(c) The gravitational force between two protons may be greater than the nuclear force between them

(d) Electromagnetic force between two protons may be greater than the nuclear force acting between them

Choose the correct option:

1. (a), (b) and (c)

2. (b), (c) and (d)

3. (a), (b) and (d)

4. All of these

If all matter were made of electrically neutral particles such as neutrons,

(a) there would be no force of friction

(b) there would be no tension in the string

(c) it would not be possible to sit on a chair

(d) the earth could not move around the sun

Choose the correct option:

1. (a), (b) and (c)

2. (a), (c) and (d)

3. (b), (c) and (d)

4. All of these

Which of the following systems may be adequately described by classical physics?

Choose the correct option: