Questions
The correct relation between joule and erg is:
- $1\ J = 10^{-5} erg$
- $1\ J = 10^{5} erg$
- $1\ J = 10^{-7} erg$
- $1\ J = 10^{7} erg$
State the wrong statement
- Total work done by internal force in a system is always zero
- Work done is different as seen from different frames of reference
- In the absence of external forces and non-conservation force , the molecules energy of a system remains conserved
- a non conservation force always do negative work
A force $\vec {F} = -k(x\hat {i} + y\hat {j})$, where $k$ is positive constant, acts on a particle moving in the $x-y$ plane. Starting from the origin, the particle is taken along the positive x-axis to the point $(a, 0)$ and then parallel to the y-axis to the point $(a, a)$.
- Work done by the force in moving particle along x-axis is $-\dfrac {1}{2}ka^{2}$
- Work done by the force in moving particle along x-axis is $-ka^{2}$
- Work done by the force in moving particle along y-axis is $-\dfrac {1}{2}ka^{2}$
- Total work done by the force for overall motion is $-ka^{2}$
A man carries a load on his head through a distance of 5 m. The maximum amount of work is done when he
- Movies it over an inclined plane
- Movies it over a horizontal surface
- Lift it vertically upwards
- All of the above
A force of $5 N$ is applied on a $20 kg$ mass at rest. the work done in the third second is:-
- $\dfrac{25}{8}J$
- $\dfrac{25}{4}J$
- $12 J$
- $25 J$
A small ball bearing is releases at the top of a long vertical column of glycerine of height $2h$. The ball bearing falls through a height $h$ in a time $t _{1}$ and then the remaining height with the terminal velocity in time $t _{2}$ Let $W _{1}$ and $W _{2}$ be the work done against viscous drag over these height. therefore.
- $t _{1}< t _{2}$
- $t _{1}> t _{2}$
- $W _{1}=W _{2}$
- $W _{1}< W _{2}$
No work is done by a force on an object if
- the force is always perpendicular to its velocity
- the force is always perpendicular to its acceleration
- the object is stationary but the point of application of the force moves on the object
- the object moves in such a way that the point of application of the force remains fixed.
A moving particle is acted upon by several forces $F _1, F _2, F _3 .....$ etc. One of the force is chosen, say $F _2$, then which of the following statement about $F _2$ will be true.
- Work done by $F _2$ will be negative if speed of the particle decreases
- Work done by $F _2$ will be positive if speed of the particle increases
- Work done by $F _2$ will be equal to the work done by other forces if speed of the particle does not change
- If $F _2$ is a conservative force, then work done by all other forces will be equal to change in potential energy due to force $F _2$ when speed remains constant.
The unit kg m$^2$s$^{-2}$ is associated with :
- work only
- kinetic energy only
- potential energy only
- all the above
1 J is equal to
- ${10}^{5}$ erg
- ${10}^{7}$ erg
- ${10}^{-7}$ erg
- none of these
The c.g.s. unit of work is
- N
- dyne
- erg
- J
One erg is equal to
- $1 g cm s^{-2}$
- 1 Nm
- $10^7 J$
- $10^{-7}J$
Select the correct statement for work, heat and change in internal energy
- Heat supplied and work done depends on initial and final states
- Change in internal energy depends on the initial and final states only
- Heat and work depend on the path between the two points
- All of these
How many electron volts make one Joule?
- $ 3.25 \times 10^{19} \mathrm{eV} $
- $ 6.25 \times 10^{18} \mathrm{eV} $
- $ 9.25 \times 10^{17} \mathrm{eV} $
- $ 1.25 \times 10^{20} \mathrm{eV} $
Water falls from a height of $210, m$. Assuming whole of energy due to fall is converted into heat the rise in temperature of water would be
($J = 4.3$ Joule/cal)
- $42^0\, C$
- $49^0\, C$
- $0.49^0\, C$
- $4.9^0\, C$
1 J Is equal to $1 : kg : m : s^{-2}$
- True
- False
- Ambiguous
- Data insufficient
Which of the following will give $1J$ of work?
- $F=1N,S=1m,\theta={0}^{0}$
- $F=1N,S=1m,\theta={90}^{0}$
- $F=0.1N,S=1m,\theta={0}^{0}$
- $F=0.1N,S=10m,\theta={90}^{0}$
$4.0\times{10}^{-19}J=$
- $1eV$
- $2eV$
- $2.5eV$
- $5eV$