A given object takes n times as much times to slide down a 45° rough incline as its takes to slide down a perfectly smooth 45° incline. The coefficient f kinetic friction between the objects and incline is given by.
23%
$ 1 - \frac {1}{n^2}$
23%
$\frac { 1}{1- n^2}$
44%
$ \sqrt {1 - \frac {1}{n^2}}$
10%
$\sqrt {\frac { 1}{1- n^2}}$
Q.2.
According to Newton’s third law all forces come in action-reaction pairs which
28%
may act on the same object.
15%
always act in the same direction.
8%
may be at right angles to each other.
48%
always act on different objects.
Q.3.
The tension in cable supporting an elevator is equal to the weight of the elevator’s elevator may be
(more than one correct)
12%
going up with increasing speed
19%
going down with increasing speed
46%
going up with uniform speed
23%
going down with uniform speed.correct
Q.4.
When train stops, the passenger move forward. It is due to
52%
inertia of passenger
33%
inertia of train
6%
gravitational pull by earth
9%
None of the above
Q.5.
A smooth wedge A is fitted in a chamber hanging from a fixed ceiling near the earth’s surface. A block B placed at the top of the wedge takes time T to slide down the length of the wedge and the cable supporting the chamber is broken ath the same instant, the block will be
22%
take a time longer than T to slide down the wedge
32%
take a time shorter than T to slide down the wedge
27%
jump off the wedge
19%
remain at the top of the wedge
Q.6.
A IITJEE text book of mass M rests flat on a horizontal table of mass m placed on the ground. Let RX->Y be the constant force exerted by the body x on body Y.Which of the following is true for the forces Rground->table and Rtable->ground
(More than one correct)
38%
It is action and reaction pair
22%
have equal magnitudecorrect
27%
Opposite directioncorrect
13%
Have resultant zerocorrect
Q.7.
Assertion and Reason
(a) If both assertion and reason are true and reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but reason is not correct explanation of the assertion.
(c) If assertion is true, but reason is false.
(d) If both assertion and reason are false.
(e) If reason is true but assertion is false.
Assertion: On a rainy day, it is difficult to drive a car or bus at high speed.
Reason: The value of coefficient of friction is lowered on wetting surface.
47%
a
17%
b
25%
c
6%
d
6%
e
Q.8.
The coefficient of static and kinetic friction between a body and the surface are .75 and .50 respectively. A force is applied to the body to make it just slide with a constant acceleration which is
38%
g/4
38%
g/2
15%
3g/4
8%
g
Q.9.
(a) If both assertion and reason are true and reason is thecorrect explanation of the assertion.
(b) If both assertion and reason are true but reason is not correct explanation of the assertion.
(c) If assertion is true, but reason is false.
(d) If both assertion and reason are false.
(e) If reason is true but assertion is false.
Assertion: Linear momentum of a body changes even when it is moving uniformly in a circle.
Reason: In uniform circular motion velocity remains constant.
26%
a
31%
b
20%
c
6%
d
17%
e
Q.10.
A skydiver jumps from a high-flying plane. When she reaches her terminal velocity
11%
the force of gravity on her is zero.
41%
her acceleration has reached magnitude g.
18%
the drag force of the air on her has become zero.
30%
the net force on her is zero.
Q.11.
A block of mass m is placed on a smooth wedge of inclination $\theta$. The whole system is accelerated horizontally so that the block does not slip on the wedge. The force exerted by the wedge on the block will be (g is acceleration due to gravity)
34%
$mgcos \theta$
16%
mg
25%
$mg sin \theta$
25%
$\frac {mg}{cos \theta}$
Q.12.
A hockey player is moving northward and suddenly turns westward with the same speed to avoid an opponent. The force that acts on
the player is
23%
frictional force along westward.
19%
muscle force along southward.
42%
frictional force along south-west
16%
muscle force along south-west.
Q.13.
By means of rope ,a body of weight W is moved vertically upward with constant acceleration a.Find the tensile force in the rope
38%
$W(1+ \frac {a}{g})$
35%
$W(1- \frac {a}{g})$
11%
W
16%
$\frac {Wa}{g}$
Q.14.
A rockets works on the principle of conservation of
55%
Linear momentum
3%
Mass
16%
Energy
26%
angular momentum
Q.15.
A uniform chain of length L is lying on the horizontal surface of a table. If the coefficient of friction between the chain and the tabletop is μ what is the maximum length of the chain that can hang over the edge of the table without disturbing the rest of the chain on table
19%
$\frac {L}{(1+\mu)}$
44%
$\frac {\mu L}{(1+\mu)}$
33%
$\frac {L}{(1-\mu)}$
4%
$\frac {\mu L}{(1-\mu)}$
Q.16.
If the normal force is doubled, the coefficient of friction, is
24%
doubled
9%
tripled
26%
halved
41%
not changed
Q.17.
A flat car of weight W roll without resistance along on a horizontal track .Initially the car together with weight w is moving to the right with speed v.What increment of the velocity car will obtain if man runs with speed relative to the floor of the car and jumps off at the left?
16%
$\frac {wu}{w+W}$
28%
$\frac {Wu}{W+w}$
48%
$\frac {(W+w)u}{w}$
8%
$\frac {(W+w)u}{2w}$
Q.18.
A car is moving with uniform velocity on a rough horizontal road. Therefore, according to Newton's first law of motion
17%
No force is being applied by its engine
21%
An acceleration is being produced in the car
31%
The kinetic energy of the car is increasing
31%
force is surely being applied by its engine
Q.19.
A coin is dropped in a lift. It takes time a to reach the floor, when lift is stationary. It takes time b, when lift is moving up with constant acceleration. Then,
23%
a > b
20%
b > a
37%
a=b
20%
none of the above
Q.20.
A reference frame attached to the earth
(more than one correct)
16%
is an inertial frame by definition
34%
Cannot be inertial frame as earth is resolving around the sun
31%
is an inertial frame because Newton's law are applicable in this frame
19%
Cannot be inertial frame because earth is rotating about its own axiscorrect
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