Force

Q. An electron is moving in the north direction. It experiences a force in the vertically upward direction. The magnetic field in that region is towards?

1. East
2. West
3. North
4. South

Q.

Can work done by a body be negative or positive?

Q. In the given figure the electron enters into the magnetic field. It deflects towards

1. Positive x-direction
2. Negative x-direction
3. Positive y-direction
4. Negative y-direction

Q. Question 10
Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?

Q. Which of the following relations is correct?

1. $r=\frac{mv}{qB}$
2. $r=\frac{qB}{mv}$
3. $r=\frac{mq}{vB}$
4. $r=\frac{mB}{qv}$

Q.

A bullet of mass $0.1kg$ is fired with the speed of $100\frac{m}{s}$, the mass of the gun being $50kg$. The velocity of recoil is:

1. $0.05\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$

2. $0.5\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$

3. $0.2\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$

4. $0.1\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$

Q. When a positively charged particle enters a uniform magnetic field perpendicular to the magnetic field, then the path of the particle will be?

1. Circular
2. Elliptical
3. Helical
4. Straight

Q.

Why anticlockwise motion is positive and clockiwse motion is negative

Q.

1 N is the force which produces an acceleration of 1 ${ms}^{-1}$​ in a body of mass 1 kg.

1. True

2. False

Q.

An electron traveling north enters a region where the electric field is uniform and points North. The electron:

Q. An electron at point A in the figure has a speed $V_0$ of magnitude $1.41\times {10}^{6}m/s$. It enters into a uniform magnetic field and follows a semicircular path in it as shown.


The magnitude of the magnetic field that will cause the electron to follow the semicircular path from A to B is?

1. $1.60\times {10}^{-4}T$
2. $1.60\times {10}^{-2}T$
3. $1.6T$
4. $1.60\times {10}^{-3}T$

Q.

How much force is needed to produce an acceleration of $2.5m/s^2$ in a body of mass $4.0kg$?

Q.

Question 3
A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is
(a) towards south
(b) towards east
(c) downward
(d) upward

Q.

When a footballer kicks a ball, the ball moves in the direction of applied force. The footballer also experiences a force on his leg which is equal to the force he exerted on the ball.

1. the football player did not hit the ball hard

2. velocity of ball is proportional to the force acting on it

Q.

We prefer to use a long spanner to loosen a tight nut.

1. True
2. False

Q. Which of the following statements is incorrect for a charged particle projected perpendicularly in a magnetic field?

1. Its kinetic energy remains constant
2. Its momentum remains constant
3. Its speed remains constant
4. Its velocity will change

Q.

A truck of mass 1000 kg moving with a velocity of 40 ${kmh}^{-1}$collides with a tree and comes to stop in 5 s. What will be the force exerted by a car on the tree?

1. (-) 2222 N

2. (-) 2242 N

3. 2000 N

4. (-) 2000 N

Q.

Question 2
If the key in the arrangement (Figure) is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are
(a) concentric circles
(b) elliptical in shape
(c) straight lines parallel to each other
(d) concentric circles near the point O but of elliptical shapes as we go away from it

Q. An electron enters in a magnetic field of intensity 5T with a velocity $2\times {10}^{7}m/s$ in a direction perpendicular to the field. Calculate the force on the electron.[charge on electron is $-1.6\times {10}^{-19}C$]

1. $2.0\times {10}^{-10}T$
2. $1.6\times {10}^{-11}T$
3. $2.5\times {10}^{-8}T$
4. $0.4\times {10}^{-11}T$

Q.

Which of the following property of a proton can change while it moves freely in a magnetic field?

1. Mass

2. Speed

3. Velocity

4. None of these

Q.

A wire carrying a current of $5A$is placed perpendicular to a magnetic induction of$2T$. The force on each $centimetre$of the wire is

1. $0.1N$

2. $100N$

3. 10 N

4. 1 N

Q.

A force of $100N$ acts on a particle of mass $25kg$. Find the acceleration of the particle.

Q. A proton and an alpha- particle moving with same velocity enter into a magnetic field acting normal to plane of their motion. Calculate ratio of radii of circular path described by proton and alpha-particle.

Q. An electron is moving with a uniform speed in the X - Y plane in a straight path along the negative X direction. If a uniform magnetic field is applied parallel along the positive z-axis, the electron will :

1. Remain unaffected
2. Speed up along the X direction
3. Start moving in the Y direction
4. Start moving in a circular path in the X-Y plane

Q. A wire is lying horizontally in the north-south direction and there is a horizontal magnetic field pointing towards the east. Some positive charges in the wire move north and an equal number of negative charges move south. The direction of the force on the wire will be?

1. East
2. Down, into the page
3. Up, out of the page
4. West

Q. A particle with charge $2\mu C$, moving with velocity $2\times {10}^{6}m/s$, enters normally in a magnetic field of 4T. The force experienced by the particle is?

1. 4 N
2. 8 N
3. 12 N
4. 16 N

Q. If an alpha-particle and a proton are projected in a magnetic field, perpendicular to field with same linear momentum then the ratio of radii of alpha-particle with proton is

Q. Which of the following CAN NOT be a possible effect of a force acting on an object?

1. It can change the direction of motion of the object.
2. It can change the speed of the object.
3. It can change the shape and size of the object.
4. It can change the material and colour of the object.

Q. A plotting compass is placed close to a current carrying wire as shown in the figure. Which of the following compasses rightly depicts the direction of needle inside the compass?

1. 
2. 
3. 
4. 

Q.

A uniform magnetic field exists in the plane of paper pointing from left to right as shown in the figure. In the field, an electron and a proton move as shown. The electron and the proton experience?

1. Forces both pointing into the plane of the paper.
2. Forces both pointing out of the plane of the paper.
3. Force pointing into the plane of the paper and out of the plane of the paper, respectively.
4. Force pointing opposite and along the direction of the uniform magnetic field respectively.