Rotational Motion Quiz-20
Dear Readers,
As per analysis for previous years, it has been observed that students preparing for NEET find Physics out of all the sections to be complex to handle and the majority of them are not able to comprehend the reason behind it. This problem arises especially because these aspirants appearing for the examination are more inclined to have a keen interest in Biology due to their medical background. Furthermore, sections such as Physics are dominantly based on theories, laws, numerical in comparison to a section of Biology which is more of fact-based, life sciences, and includes substantial explanations. By using the table given below, you easily and directly access to the topics and respective links of MCQs. Moreover, to make learning smooth and efficient, all the questions come with their supportive solutions to make utilization of time even more productive. Students will be covered for all their studies as the topics are available from basics to even the most advanced.
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Q1. Two bodies are projected from roof with same speed in different directions. If air resistance is not taken into account then?
Solution
In the case of projectile motion, if bodies are projected with same speed, they reached at ground with same speeds. So, if bodies have same mass, then momentum of bodies or magnitude of momenta must be same
In the case of projectile motion, if bodies are projected with same speed, they reached at ground with same speeds. So, if bodies have same mass, then momentum of bodies or magnitude of momenta must be same
Q2. When a meteorite burns in the atmosphere, then ?
Solution
The conservation principle of momentum is applicable to a system consisting of meteorites, earth and air molecules
The conservation principle of momentum is applicable to a system consisting of meteorites, earth and air molecules
Q3. A ball moving with a certain velocity hits another identical ball at rest. If the plane is frictionless and collision is elastic, the angle between the directions in which the balls move after collision, will be?
Solution
This is an example of elastic oblique collision. When a moving body collides obliquely with another identical body in rest, then during elastic collision, the angle of divergence will be 90°.
This is an example of elastic oblique collision. When a moving body collides obliquely with another identical body in rest, then during elastic collision, the angle of divergence will be 90°.
Q4. A ring of mass m and radius r is melted and then moulded into a sphere. The moment of inertia of the sphere will be?
Solution
Less than that of the ring
Less than that of the ring
Q5. A small object of mass m is attached to a light string which passes through a hollow tube. The tube is hold by one hand and the string by the other. The object is set into rotation in a circle of radius R and velocity v. The string is then pulled down, shortening the radius of path of r. What is conserved?
Solution
In the absence of external torque angular momentum remains constant
In the absence of external torque angular momentum remains constant
Q6. Three identical balls A,B and C are lying on a horizontal frictionless table as shown in figure. If ball A is imparted a velocity v towards B and C and the collisions are perfectly elastic, then finally?
Solution
When two identical balls collide head on elastically, they exchange their velocities. Hence when A collides with B, A transfers its whole velocity to B. When B collides with C, B transfers its whole velocity to C. Hence finally A and B will be at rest and only C will be moving forward with speed v
When two identical balls collide head on elastically, they exchange their velocities. Hence when A collides with B, A transfers its whole velocity to B. When B collides with C, B transfers its whole velocity to C. Hence finally A and B will be at rest and only C will be moving forward with speed v
Q7. A solid sphere of mass 500 g and radius 10 cm rolls without slipping with the velocity 20 cm/s. The total kinetic energy of the sphere will be?
Solution
1/2 mv2 (1+K2/R2 )=1/2 (0.5) (0.2)2 (1+2/5)=0.014 J
1/2 mv2 (1+K2/R2 )=1/2 (0.5) (0.2)2 (1+2/5)=0.014 J
Q8. A wheel of moment of inertia 2.5 Kg-m2 has an initial angular velocity of 40 rads-1. A constant torque of 10 Nm acts on the wheel. The time during which the wheel is accelerated to 60 rads-1 is?
Solution
Given, MI=2.5 kgm-2 W=40 rad s-1 T=10 Nm As T=Iα 10=2.5α α=4 rad s-2 Now, ω=ω0+αt 60=40+4×t 20=4t t=5 s
Given, MI=2.5 kgm-2 W=40 rad s-1 T=10 Nm As T=Iα 10=2.5α α=4 rad s-2 Now, ω=ω0+αt 60=40+4×t 20=4t t=5 s
Q9. A body of mass M at rest explodes into three pieces, two of which of mass M/4 each are thrown off in mutually perpendicular directions with speeds of 3ms-1 and 4ms-1 respectively. Then the third piece will be thrown off with a speed of?
Solution
As there is no external force, hence p =p 1+p 2+p 3= constant ⇒ |p 3 |=|p 1+p 2 |=m/4 √((3)2+(4)2 )=5m/4 [since v1 and v2 are mutually perpendicular] ∴ p3=m/2 v3=5m/4 ⇒ v3=5/2=2.5ms-1
As there is no external force, hence p =p 1+p 2+p 3= constant ⇒ |p 3 |=|p 1+p 2 |=m/4 √((3)2+(4)2 )=5m/4 [since v1 and v2 are mutually perpendicular] ∴ p3=m/2 v3=5m/4 ⇒ v3=5/2=2.5ms-1
Q10. A bullet of mass M hits a block of mass M'. The transfer to energy is maximum, when?
Solution
If M=M' then bullet will transfer whole of its velocity (and consequently 100% of its KE) to block and will itself come to rest as per theory of collision.
If M=M' then bullet will transfer whole of its velocity (and consequently 100% of its KE) to block and will itself come to rest as per theory of collision.
