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Physics MCQ Help
- Thread starter darkpichu
- Start date
- Messages
- 1,148
- Reaction score
- 166
- Points
- 73
Its better that you try to think yourself first, if still nothing comes into your mind then ask. If one concept doesn't fit in apply some other one and like that you will be able to get the answer.
Q10)
in elastic collision kinetic energy is conserved and in inelastic collision kinetic energy is not conserved.
Exp 1:
energy before the collision: 1/2mv^2 + 0 = 1/2mv^2
energy after the collision: 0 + 1/2mv^2 = 1/2mv^2
energies are conserved, collision elastic
Exp 2:
energy before the collision: 1/2m1v^2 + 0 = 1/2m2v^2
energy after the collision: 1/2(m1+m2)v^2
energies not conserved, collision inelastic
remember whenever two objects stick together or fuse, the collision is always inelastic.
Q11)
There is air resistance so x component of velocity will decreases until it reaches zero (there is no acceleration acting on x direction) and y component of velocity will increase until it reaches its terminal velocity (When weight equals air resistance) (there is initial acceleration of 9.81 acting on y component)
Q14)
clockwise moment: 15 x 3= 45 Nm
anticlockwise moment: 5 x 2 + 10 x 2= 30 Nm
resultant moment: 45-30 = 15 Nm clockwise
Q17)
rate of change of energy is power
Power=Fv
where:
resultant F=(m1-m2)g
P=(m1-m2)gv
Q21)
Let Force exerted by load be W
let K1 be the spring constant of wire X and K2 be the spring constant of wire Y
because wires are joint and of different length and spring constant, different ratio of forces will act on both of them.
Force on X=3/(3+1) W=3/4 W
Force on Y=1/4 W
For the 1st wire:
X:
3/4 W= K1 (1.5)
k1 = 1/2W
Y:
1/4W=K2 (1)
K2=1/4W
For the 2nd wire:
lengths of wires have changes so will the ratio of forces acting on them
X:
1/4W=K1 x1 where k1=1/2W
1/4W=1/2W x1
x1=1/2 mm
Y:
3/4W=K2 x2 where k2=1/4W
3/4W=1/4W x2
x2=3 mm
total extension=x1 + x2= 0.5 + 3= 3.5 mm
Q22)
All the statements are wrong.
statement 1: solid are rigid because there are stronger forces of attraction between them and are held in fixed pattern
statement 2: liquid flows because there are weaker forces of attraction between molecules. Collisions between the particles a strong enough to force the particles apart
statement 3: gases are less dense because particles are further apart.
Q25)
wave is moving to right so particles will displace to the left. C will be the point which will move upward and with greatest velocity as it is at the equilibrium. D will also move upward but its velocity will not be max.
A and B will move downward.
Q37)
combined resistance of series: 3 x 10= 30 Ω
combined resistance of parallel: 1/R=1/10 + 1/30
R=7.5 Ω
Q10)
in elastic collision kinetic energy is conserved and in inelastic collision kinetic energy is not conserved.
Exp 1:
energy before the collision: 1/2mv^2 + 0 = 1/2mv^2
energy after the collision: 0 + 1/2mv^2 = 1/2mv^2
energies are conserved, collision elastic
Exp 2:
energy before the collision: 1/2m1v^2 + 0 = 1/2m2v^2
energy after the collision: 1/2(m1+m2)v^2
energies not conserved, collision inelastic
remember whenever two objects stick together or fuse, the collision is always inelastic.
Q11)
There is air resistance so x component of velocity will decreases until it reaches zero (there is no acceleration acting on x direction) and y component of velocity will increase until it reaches its terminal velocity (When weight equals air resistance) (there is initial acceleration of 9.81 acting on y component)
Q14)
clockwise moment: 15 x 3= 45 Nm
anticlockwise moment: 5 x 2 + 10 x 2= 30 Nm
resultant moment: 45-30 = 15 Nm clockwise
Q17)
rate of change of energy is power
Power=Fv
where:
resultant F=(m1-m2)g
P=(m1-m2)gv
Q21)
Let Force exerted by load be W
let K1 be the spring constant of wire X and K2 be the spring constant of wire Y
because wires are joint and of different length and spring constant, different ratio of forces will act on both of them.
Force on X=3/(3+1) W=3/4 W
Force on Y=1/4 W
For the 1st wire:
X:
3/4 W= K1 (1.5)
k1 = 1/2W
Y:
1/4W=K2 (1)
K2=1/4W
For the 2nd wire:
lengths of wires have changes so will the ratio of forces acting on them
X:
1/4W=K1 x1 where k1=1/2W
1/4W=1/2W x1
x1=1/2 mm
Y:
3/4W=K2 x2 where k2=1/4W
3/4W=1/4W x2
x2=3 mm
total extension=x1 + x2= 0.5 + 3= 3.5 mm
Q22)
All the statements are wrong.
statement 1: solid are rigid because there are stronger forces of attraction between them and are held in fixed pattern
statement 2: liquid flows because there are weaker forces of attraction between molecules. Collisions between the particles a strong enough to force the particles apart
statement 3: gases are less dense because particles are further apart.
Q25)
wave is moving to right so particles will displace to the left. C will be the point which will move upward and with greatest velocity as it is at the equilibrium. D will also move upward but its velocity will not be max.
A and B will move downward.
Q37)
combined resistance of series: 3 x 10= 30 Ω
combined resistance of parallel: 1/R=1/10 + 1/30
R=7.5 Ω
- Messages
- 1,148
- Reaction score
- 166
- Points
- 73
