Applying NLM along 3 Axis

Q.

A person standing on a spring balance inside a stationary lift measures $60kg$. The weight of that person if the lift descends with a uniform downward acceleration of $1.8m/s^2$ will be ___________ $N$. $[g=10m/s^2]$

Q.

A helicopter of mass $1000kg$ rises with a vertical acceleration of $15m/s^2$. The crew and the passengers weigh $300kg$. Give the magnitude and direction of the

1. Force on the floor by the crew and passengers.
2. Action of the rotor of the helicopter on the surrounding air.
3. Force on the helicopter due to the surrounding air.

Q.

A block of mass 2kg rests on a plane inclined at an angle of 30^o with the horizontal. The coefficient of friction between the block and the surface is 0.7. The frictional force acting on the block is

1. 10 N

2. 11 N

3. 11.9 N

4. 12.5 N

Q. 1. A student says that he had applieda force F =-k\sqrt x on a particle and the particle moved in simple harmonic motion. He refuses to tell whether k is a constant or not.Assume that he has worked only with positive x and noother force acted on the particle. (a) As x increases k increases. (b) As x increases k decreases. (c) As x increases k remains constant. (d) The motion cannot be simple harmonic.

Q. .A disc revolves in horizontal plane at a steady rate of 3 rev/s. A coin just remains on the disc if kept at a distance of 2 cm from the axis of rotation.What is the coefficient of friction between thecoin and the disc(A) 0-5(C) 0-7(B) 0-65(D) 0-75.

Q. .A block of weight 100 N is slowly slid up on a smoothincline of inclination 37^° by a person. Calculate the workdone by the person in moving the block through adistance of 2-0 m, if the driving force is (a) parallel tothe incline and (b) in the horizontal direction.

Q. .The ladder shown in figure has negligible mass and rests onfrictionless floor. A crossbar connects the two legs of theladder at the centre as shown. The angle between the twolegs is 60- The fat person sitting on the ladder has a massof 80 kg. Find the constant forces exerted by thefloor on each leg and the tension in the crossbar.1m60^° 30imSmooth

Q. A block of mass m is released on a smooth inclinedplane of inclination 0 with the horizontal. The forceexerted by the plane on the block has a magnitude

Q.

Find the minimum force P required to avoid sliding of the block of weight W on the incline plane

1. 

2. 

3. 

4. 

Q.

A balloon of mass M is descending at a constant acceleration $\alpha$. When a mass m is released from the balloon, it starts rising with the same acceleration $\alpha$. Assuming that its volume does not change, what is the value of m?

1. 

2. 

3. 

4. 

Q.

A mass of 100 kg is resting on a rough inclined plane of 60^o. If the coefficient of friction is 0.5, then the least force acting parallel to the plane to keep the mass in equilibrium is

1. 100 N

2. 603.7 N

3. 500 N

4. 605.5 N

Q.

In the figure shown, there is a smooth tube of radius 'R', fixed in the vertical plane. A ball 'B' of mass 'm' is released from the top of the tube. B slides down due to gravity and compresses the spring. The end 'C' of the spring is fixed and the end A is free. Initially the line OA makes an angle of ${60}^{\circ }$ with OC and finally it makes an angle of ${30}^{\circ }$ after compression. Find the spring constant of the spring.

1. $\frac{12mg(2+\sqrt{3})}{{\pi }^{2}R}$

2. $\frac{36mg(2+\sqrt{3})}{{\pi }^{2}R}$

3. None of these

4. $\frac{36mg(2+\sqrt{3})}{{\pi }^{2}R}$

Q. A man of mass 70 kg stands on a weighing scale in a lift which is moving (a) upwards with a uniform speed of 10 m s-1, (b) downwards with a uniform acceleration of 5 m s-2, (c) upwards with a uniform acceleration of 5 m s-2. What would be the readings on the scale in each case? (d) What would be the reading if the lift mechanism failed and it hurtled down freely under gravity ?

Q. A force F=(3ti + 4t^2 j) N acts on an object moving in XY-plane. The change in momentum of the object in time interval t = 0 to t = 2s

Q.

Tension on an almost massless rope being pulled by two boys, one small and one big, will be

1. none of the above

2. more on the small boy end

3. same along the length of entire length of the rope

4. more on the big boy end

Q. When an object is in equilibrium state, then

1. It must be at rest
2. No force is acting on it
3. It's net acceleration must be zero
4. All of these

Q.

Three astronauts, propelled by jet backpacks, push and guide a 2kg asteroid toward a processing dock, exerting the forces shown in figure, with $F_1=4N,F_2=4N,F_3=4N,{\theta }_1={30}^{\circ }and{\theta }_3={60}^{\circ }$. What is the asteroid's acceleration in unit-vector notation ?

1. $(\sqrt{3}+1)\hat{i}+2\hat{j}$

2. $2\sqrt{3}\hat{i}+2\hat{j}$

3. $(3+\sqrt{3})\hat{i}+(1-\sqrt{3})\hat{j}$

4. $4\sqrt{3\hat{i}}+8\hat{j}$

Q.

why cricket player lowers his hands while catching a cricket ball?

Q. 92.A ball of mass m moving with velocity v strikes a wall normally and returns without loss of energy. The variation of force on the ball by the wall with time has been shown in yhe figure. Value of Fo is

Q.

when a ball is thrown vertically upward its momentum first decreases and then increases. is conservation of momentum violeted in this process?

Q. suppose the acceleration due to gravity at a place is 10m/s2. Find its value in cm/(minute)

Q. 24.The equation of motion of a particle projected obliquely from the ground under gravity us given by= 2x - x² where x and y are in Meyer The intital speed of projection is

Q.

Two persons each of mass m are standing at the two extremes of a railroad car of mass M resting on a smooth track (figure). The person on left jumps to the left with a horizontal speed u with respect to the state of the car before the jump. Therefore, the other person jumps to the right, again with the same horizontal speed u with respect to the state of the car before his jump. Find the velocity of the car after both the persons have jumped off.

1. towards left

2. towards left

3. towards right

4. towards right

Q. One end of a string of length $l$ is connected to a particle of mass $m$ and the other to a small peg on a smooth horizontal table. If the particle moves in a circle with speed $v$ the net force on the particle ( directed towards the centre ) is :

1. $T$
2. $T+\frac{m{v}^2}{l}$
3. $T-\frac{m{v}^2}{l}$
4. $0$

Q.

A boy of mass 50 kg is standing on a weighing machine placed on the floor of a lift. The machine reads his weight in newton. What is the reading of the machine when the lift is stationary? Take $g=9.8m{s}^{-2}$

1. Zero

2. 50 N

3. 490 N

4. 500 N

Q. In the figure, a force $F=20\text{N}$ is applied on block $\text{A}$. What would be the acceleration of the block $\text{B}$ after $10$ seconds from the start. Assume all surfaces are smooth.

1. $\frac{10}{6}{\text{m/s}}^2$
2. $2{\text{m/s}}^2$
3. zero
4. cannot be calculated

Q. A pebbal of mass 0.05 is thrown vertical upwards. Given the direction and magnitude of the net force on the pebbal :
a) During its upward motion b) During its downward motion

Q. A disc revolves in horizontal plane at a steady rate of 3 rev/s. A coin just remains on the disc ifkept at a distance of 2 cm from the axis of rotation.What is the coefficient of friction between thecoin and the disc?(A) 0-5(C) 0.7(B) 0-65(D) 0-75

Q. A block of mass 25 kg is raised by a 50 kg man in two different ways as shown in Fig. 5.19. What is the action on the floor by the man in the two cases ? If the floor yields to a normal force of 700 N, which mode should the man adopt to lift the block without the floor yielding ?

Q. an object of mass 2 kg is sliding with a cons†an t velocity of 4 m/s on a rough horizontal table under the action of 4 N horizontal force . if a 10 N force is applied instead of 4 N then the accelaration of the block is