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Work, Power & Energy

238 Questions Start Errorless Test
All Exams Allen Advance Errorless
AIEEE 2009 Q151 Errorless 8. Graphical Questions MCQ
Consider a rubber ball freely falling from a height h=4.9m onto a horizontal elastic plate. Assume that the duration of collision is negligible and the collision with the plate is totally elastic. Then the velocity as a function of time and the height as a function of time will be
A.

B.

C.

D.

WB-JEE 2008 Q152 Errorless 2. Work Done by Variable Force MCQ
A wire is stretched under a force. If the wire suddenly snaps the temperature of the wire
A.
Remains the same
B.
Decreases
C.
Increases
D.
First decreases then increases
Kerala PET 2008 Q153 Errorless 3. Conservation of Energy and Momentum MCQ
A spring gun of spring constant 90 N/cm is compressed 12 cm by a ball of mass 16 g. If the trigger is pulled, the velocity of the ball is
A.
$50 \mathrm{~ms}^{-1}$
B.
$9 \mathrm{~ms}^{-1}$
C.
$40 \mathrm{~ms}^{-1}$
D.
$60 \mathrm{~ms}^{-1}$
E.
$90 \mathrm{~ms}^{-1}$
Kerala PET 2008 Q154 Errorless 3. Conservation of Energy and Momentum MCQ
A bullet of mass 0.05 kg moving with a speed of $80 \, ms^{-1}$ enters a wooden block and is stopped after a distance of 0.40 m. The average resistive force exerted by the block on the bullet is
A.
300 N
B.
20 N
C.
400 N
D.
40 N
E.
200 N
AIEEE 2008 Q155 Errorless 3. Conservation of Energy and Momentum MCQ
An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range
A.
$2 \times 10^{5} J - 3 \times 10^{5} J$
B.
20,000 J - 50,000 J
C.
2,000 J - 5,000 J
D.
200 J - 500 J
CBSE PMT 2008 Q156 Errorless 4. Power MCQ
Water falls from a height of 60 m at the rate of 15 kg/s to operate a turbine. The losses due to frictional forces are 10% of energy. How much power is generated by the turbine ( $g=10\ m/s^{2}$ )
A.
12.3 kW
B.
7.0 kW
C.
8.1 kW
D.
10.2 kW
Odisha JEE 2008 Q157 Errorless 6. Perfectly Inelastic Collision MCQ
Two identical mass $M$ moving with velocity $u_{1}$ and $u_{2}$ collide perfectly inelastically. The loss in energy is
A.
$\frac{M}{2}(u_2 - u_1)^2$
B.
$\frac{M}{2}(u_1 - u_2)^2$
C.
$\frac{M}{4}(u_1 - u_2)^2$
D.
$\frac{M}{4}(u_2 - u_1)^2$
IIT-JEE 2008 Q158 Errorless 9. JEE Section MSQ
Two balls, having linear momenta $\vec{p}_1 = p\hat{i}$ and $\vec{p}_2 = -\vec{p}\hat{i}$ , undergo a collision in free space. There is no external force acting on the balls. Let $\vec{p}_1$ and $\vec{p}_2$ be their final momenta. The following option(s) is(are) NOT ALLOWED for any non-zero value of $p, a_1, a_2, b_1, b_2, c_1$ and $c_2$
A.
$\vec{p}_1 = a_1\hat{i} +b_1\hat{j} +c_1\hat{k},\vec{p}_2 = a_2\hat{i} +b_2\hat{j}$
B.
$\vec{p}_1 = c_1\hat{k}$ , $\vec{p}_2 = c_2\hat{k}$
C.
$\vec{p}_1 = a_1\hat{i} +b_1\hat{j} +c_1\hat{k},\vec{p}_2 = a_2\hat{i} +b_2\hat{j} -c_1\hat{k}$
D.
$\vec{p}_1 = a_1\hat{i} +b_1\hat{j},\vec{p}_2 = a_2\hat{i} +b_1\hat{j}$
IIT-JEE 2008 Q159 Errorless 9. JEE Section MCQ
A small block of mass M moves on a frictionless surface of an inclined plane, as shown in figure. The angle of the incline suddenly changes from $60^{\circ}$ to $30^{\circ}$ at point B. The block is initially at rest at A. Assume that collisions between the block and the incline are totally inelastic ( $g = 10 \, m/s^{2}$ ). The speed of the block at point B immediately after it strikes the second incline is
A.
$\sqrt{60}$ m/s
B.
$\sqrt{45}$ m/s
C.
$\sqrt{30}$ m/s
D.
$\sqrt{15}$ m/s
IIT-JEE 2008 Q160 Errorless 9. JEE Section MCQ
A small block of mass M moves on a frictionless surface of an inclined plane, as shown in figure. The angle of the incline suddenly changes from $60^{\circ}$ to $30^{\circ}$ at point B. The block is initially at rest at A. Assume that collisions between the block and the incline are totally inelastic ( $g = 10 \, m/s^{2}$ ). The speed of the block at point C, immediately before it leaves the second incline is
A.
$\sqrt{120} m / s$
B.
$\sqrt{105} m / s$
C.
$\sqrt{90} m / s$
D.
$\sqrt{75} m / s$
IIT-JEE 2008 Q161 Errorless 9. JEE Section MCQ
A small block of mass M moves on a frictionless surface of an inclined plane, as shown in figure. The angle of the incline suddenly changes from $60^{\circ}$ to $30^{\circ}$ at point B. The block is initially at rest at A. Assume that collisions between the block and the incline are totally inelastic ( $g = 10 \, m/s^{2}$ ). If collision between the block and the incline is completely elastic, then the vertical (upward) component of the velocity of the block at point B, immediately after it strikes the second incline is
A.
$\sqrt{30}$ m/s
B.
$\sqrt{15}$ m/s
C.
0
D.
$-\sqrt{15}$ m/s
Kerala PET 2007 Q162 Errorless 2. Work Done by Variable Force MCQ
A rod AB of mass 10kg and length 4m rests on a horizontal floor with end A fixed so as to rotate it in vertical plane about perpendicular axis passing through A. If the work done on the rod is 100J, the height to which the end B be raised vertically above the floor is
A.
1.5 m
B.
2.0 m
C.
1.0 m
D.
2.5 m
Kerala PET 2007 Q163 Errorless 3. Conservation of Energy and Momentum MCQ
A simple pendulum is released from $A$ as shown. If $m$ and $l$ represent the mass of the bob and length of the pendulum, the gain in kinetic energy at $B$ is
A.
$\frac{mgl}{2}$
B.
$\frac{mgl}{\sqrt{2}}$
C.
$\frac{\sqrt{3}}{2} mgl$
D.
$\frac{2}{\sqrt{3}} mgl$
Kerala PET 2007 Q164 Errorless 3. Conservation of Energy and Momentum MCQ
A particle is released from a height S. At certain height its kinetic energy is three times its potential energy. The height and speed of the particle at that instant are respectively
A.
$\frac{S}{4}, \frac{3gS}{2}$
B.
$\frac{S}{4}, \frac{\sqrt{3gS}}{2}$
C.
$\frac{S}{2}, \frac{\sqrt{3gS}}{2}$
D.
$\frac{S}{4} \cdot \sqrt{\frac{3gS}{2}}$
AIEEE 2007 Q165 Errorless 3. Conservation of Energy and Momentum MCQ
A 2 kg block slides on a horizontal floor with a speed of 4 m/s. It strikes a uncompressed spring, and compresses it till the block is motionless. The kinetic friction force is 15 N and spring constant is 10,000 N/m. The spring compresses by
A.
5.5 cm
B.
2.5 cm
C.
11.0 cm
D.
8.5 cm
Kerala PET 2007 Q166 Errorless 4. Power MCQ
An electric pump is used to fill an overhead tank of capacity $9m^{3}$ kept at a height of $10m$ above the ground. If the pump takes 5 minutes to fill the tank by consuming $10kW$ power the efficiency of the pump should be (Take $g = 10ms^{-2}$ )
A.
$60\%$
B.
$40\%$
C.
$20\%$
D.
$30\%$
KCET 2007 Q167 Errorless 5. Elastic and Inelastic Collision MCQ
A shell of mass 20 kg at rest explodes into two fragments whose masses are in the ratio 2 : 3. The smaller fragment moves with a velocity of $6 \, ms^{-1}$ . The kinetic energy of the larger fragment is
A.
96 J
B.
216 J
C.
144 J
D.
360 J
IIT-JEE 2007 Q168 Errorless 9. JEE Section MCQ
Statement-1 : In an elastic collision between two bodies, the relative speed of the bodies after collision is equal to the relative speed before the collision. Statement-2 : In an elastic collision, the linear momentum of the system is conserved.
A.
If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.
If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.
If assertion is true but reason is false.
D.
If the assertion and reason both are false.
E.
If assertion is false but reason is true.
IIT-JEE 2007 Q169 Errorless 9. JEE Section MCQ
Statement-1 : A block of mass m starts moving on a rough horizontal surface with a velocity v. It stops due to friction between the block and the surface after moving through a certain distance. The surface is now tilted to an angle of $30^{\circ}$ with the horizontal and the same block is made to go up on the surface with the same initial velocity v. The decrease in the mechanical energy in the second situation is smaller than that in the first situation. Statement-2 : The coefficient of friction between the block and the surface decreases with the increase in the angle of inclination
A.
If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.
If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.
If assertion is true but reason is false.
D.
If the assertion and reason both are false.
E.
If assertion is false but reason is true.
AIEEE 2006 Q170 Errorless 1. Work Done by Constant Force MCQ
A particle of mass 100g is thrown vertically upwards with a speed of 5m/s. The work done by the force of gravity during the time the particle goes up is
A.
-1.25 J
B.
1.25 J
C.
0.5 J
D.
-0.5 J
J & K CET 2006 Q171 Errorless 3. Conservation of Energy and Momentum MCQ
A body at rest breaks into two pieces with unequal mass
A.
Both of them have equal speeds
B.
Both of them move along a same line with unequal speeds
C.
Sum of their momentum is non zero
D.
They move along different lines with different speeds
J & K CET 2006 Q172 Errorless 4. Power MCQ
A body of mass 2 kg is projected at 20 m/s at an angle $60^{\circ}$ above the horizontal. Power on the block due to the gravitational force at its highest point is
A.
200 W
B.
$100\sqrt{3}$ W
C.
50 W
D.
Zero
BHU 2006 Q173 Errorless 4. Power MCQ
A body is initially at rest. It undergoes one-dimensional motion with constant acceleration. The power delivered to it at time $t$ is proportional to
A.
$t^{1/2}$
B.
$t$
C.
$t^{3/2}$
D.
$t^2$
DCE 2006 Q174 Errorless 5. Elastic and Inelastic Collision MCQ
An intense stream of water of cross-sectional area A strikes a wall at an angle $\theta$ with the normal to the wall and returns back elastically. If the density of water is $\rho$ and its velocity is v, then the force exerted in the wall will be
A.
$2 A v \rho \cos \theta$
B.
$2 A v ^ {2} \rho \cos \theta$
C.
$2 A v ^ {2} \rho$
D.
$2 A v \rho$
AIEEE 2006 Q175 Errorless 7. Critical Thinking MCQ
A mass of $Mkg$ is suspended by a weightless string, the horizontal force that is required to displace it until the string makes an angle of $45^{\circ}$ with the initial vertical direction is
A.
$Mg\sqrt{2}$
B.
$\frac{Mg}{\sqrt{2}}$
C.
$Mg(\sqrt{2} - 1)$
D.
$Mg(\sqrt{2} + 1)$