The driver of a car travelling at velocity v suddenly sees a broad wall in front of him at a distance d. He should
Brake sharply
Turn sharply
(1) and (2) both
None of the above
Which of the following graph depicts spring constant k versus length l of the spring correctly
Work done by a frictional force is
Negative
Positive
Zero
All of the above
A block of mass 50 kg slides over a horizontal distance of 1 m. If the coefficient of friction between their surfaces is 0.2, then work done against friction is
98 J
72J
56 J
34 J
A body of mass m is moving in a circle of radius r with a constant speed v. The force on the body is mv2r and is directed towards the centre. What is the work done by this force in moving the body over half the circumference of the circle
mv2πr2
mv2r2
πr2mv2
A man pushes a wall and fails to displace it. He does:
A body moves a distance of 10 m along a straight line under the action of a force of 5 N. If the work done is 25 joules, the angle which the force makes with the direction of motion of the body is
0°
30°
60°
90°
A force acts on a 30 gm particle in such a way that the position of the particle as a function of time is given by x=3t−4t2+t3, where x is in metres and t is in seconds. The work done during the first 4 seconds is
5.28 J
450 mJ
490 mJ
530 mJ
The minimum work done in pulling up a block of wood weighing 2 kN for a length of 10m on a smooth plane inclined at an angle of 15° with the horizontal is (given: sin15°=0.2588):
A body of mass 6kg is under a force which causes displacement in it given by S=t24 metres where t is time. The work done by the force in 2 seconds is-
12 J
9 J
6 J
3 J
A particle moves from position r→1= 3i^+2j^−6k^ to position r→2=14i^+13j^+9k^ under the action of force 4i^+j^+3k^ N. The work done will be
100 J
50 J
200 J
75 J
A uniform chain of length 2m is kept on a table such that a length of 60cm hangs freely from the edge of the table. The total mass of the chain is 4kg. What is the work done in pulling the entire chain on the table?
7.2 J
3.6 J
120 J
1200 J
A particle is acted upon by a force of constant magnitude which is always perpendicular to the velocity of the particle, the motion of the particle takes place in a plane. It follows that
Its velocity is constant
Its acceleration is constant
Its kinetic energy is constant
It moves in a straight line
Two bodies of masses 1 kg and 5 kg are dropped gently from the top of a tower. At a point 20 cm from the ground, both the bodies will have the same
Momentum
Kinetic energy
Velocity
Total energy
A particle moves under the effect of a force F = Cx from x = 0 to x = x1. The work done in the process is
Cx12
12Cx12
Cx1
A cord is used to lower vertically a block of mass M by a distance d with constant downward acceleration g4. Work done by the cord on the block is
Mgd4
3Mgd4
−3Mgd4
Mgd
Two springs have their force constant as k1 and k2(k1>k2). When they are stretched by the same force
No work is done in case of both the springs
Equal work is done in case of both the springs
More work is done in case of second spring
More work is done in case of first spring
The potential energy of a certain spring when stretched through a distance ‘S’ is 10 joule. The amount of work (in joule) that must be done on this spring to stretch it through an additional distance ‘S’ will be:
30
40
10
20
A spring of spring constant 5 × 103 N/m is stretched initially by 5cm from the unstretched position. Then the work required to stretch it further by another 5 cm is
12.50 N-m
6.25 N-m
18.75 N-m
25.00 N-m
A mass of 0.5kg moving with a speed of 1.5 m/s on a horizontal smooth surface, collides with a nearly weightless spring of force constant k = 50 N/m. The maximum compression of the spring would be
0.15 m
0.12 m
1.5 m
0.5 m
A particle moves in a straight line with retardation proportional to its displacement. Its loss of kinetic energy for any displacement x is proportional to-
x2
ex
x
loge x
The spring extends by x on loading, then energy stored by the spring is : (if T is the tension in spring and k is spring constant)
T22k
T22k2
2kT2
2T2k
The potential energy of a body is given by, U = A – Bx2 (Where x is the displacement). The magnitude of force acting on the particle is
Constant
Proportional to x
Proportional to x2
Inversely proportional to x
The potential energy between two atoms in a molecule is given by U(x)=ax12−bx6; where a and b are positive constants and x is the distance between the atoms. The atoms are in stable equilibrium when:
x=11a5b6
x=a2b6
x = 0
x=2ab6
Which one of the following is not a conservative force
Gravitational force
Electrostatic force between two charges
Magnetic force between two magnetic dipoles
Frictional force
Work done in raising a box depends on
How fast it is raised
The strength of the man
The height by which it is raised
If the kinetic energy of a body becomes four times of its initial value, then new momentum will
Becomes twice its initial value
Become three times its initial value
Become four times its initial value
Remains constant
If the water falls from a dam into a turbine wheel 19.6 m below, then the velocity of water at the turbine is (g = 9.8 m/s2)
9.8 m/s
19.6 m/s
39.2 m/s
98.0 m/s
Two identical cylindrical vessels with their bases at the same level each contain a liquid of density; ρ. The height of the liquid in one vessel is h1 and that in the other vessel is h2 h1>h2.The area of either base is A. The work done by gravity in equalizing the levels when the two vessels are connected is :
(h1−h2)gρ
(h1−h2)gAρ
12(h1−h2)2gAρ
14(h1−h2)2gAρ
If the increase in the kinetic energy of a body is 22%, then the increase in the momentum will be
22%
44%
10%
300%
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