A man pushes a wall and fails to displace it. He does:
1. negative work
2. positive but not maximum work
3. no work at all
4. maximum work

A body constrained to move along the \({z}\)-axis of a coordinate system is subjected to constant force given by \(\vec{F}=-\hat{i}+2 \hat{j}+3 \hat{k}\) where \(\hat{i},\hat{j} \) and \(\hat{k}\) are unit vectors along the \({x}\)-axis, \({y}\)-axis and \({z}\)-axis of the system respectively. The work done by this force in moving the body a distance of \(4~\text m\) along the \({z}\)-axis will be:
1. \(15~\text J\) 
2. \(14~\text J\) 
3. \(13~\text J\) 
4. \(12~\text J\) 

A block of mass \(m\) is being lowered by means of a string attached to it. The system moves down with a constant velocity. Then:
                                          

Which of the following is not a unit of energy?
1. watt-hour
2. joule
3. eV
4. N/m

A particle of mass m₁ is moving with a velocity v₁ and another particle of mass m₂ is moving with a velocity v₂. Both of them have the same momentum, but their kinetic energies are E₁ and E₂ respectively. If m₁ > m₂ then: 

1. $\frac{{\mathrm{E}}_1}{{\mathrm{E}}_2}=\frac{{\mathrm{m}}_1}{{\mathrm{m}}_2}$

2. ${\mathrm{E}}_1>{\mathrm{E}}_2$

3. ${\mathrm{E}}_1={\mathrm{E}}_2$

4. ${\mathrm{E}}_1<{\mathrm{E}}_2$

A rigid body of mass \(m\) is moving in a circle of radius \(r\) with constant speed \(v.\) The force on the body is \(\frac{mv^2}{r}\) and is always directed towards the center. The work done by this force in moving the body over half the circumference of the circle will be:

1. \(\frac{mv^{2}}{rπ}\) 
2. \(mr^{2} \pi\)
3. zero
4. \(2 mv^{2} \pi\)$\mathrm{}$

The kinetic energy of a body is increased by 21%. The percentage increase in the magnitude of linear momentum of the body will be:

1.  10%

2.  20%

3.  Zero

4.  11.5%

A person of mass \(m\) ascends the stairs and goes up slowly through a height \(h\). Then,

Mark the correct statement(s):

1. Internal forces cannot increase the kinetic energy of a system.

2. Internal forces may increase the kinetic energy of a system.

3. Work done by kinetic friction is always negative.

4. Both (2) & (3)

Work done by frictional force during the walking of a man is:
1. positive
2. negative
3. zero
4. maybe positive or negative