Friction and Horizontal Circular Motion Problems

Q.

A car goes around a flat curved road. Which of the following can provide for the centripetal force?

1. Electrostatic attraction

2. Friction

3. Weight

4. Air resistance

Q.

A block of mass m is revolving in a smooth horizontal plane with a constant speed v. If the radius of the circular path is R, find the total contact force received by the block.

1. 

2. mg

3. 

4. 

Q.

A coin is pushed down tangentially from an angular position $\theta$ on a cylindrical surface, with a velocity v as shown in the figure. If the coefficient of friction between the coin and surface is $\mu$, find the tangential acceleration of the coin.

1. g(sin - cos )

2. 

3. 

4. 

Q. Assertion :If the net external force on the body is zero, then its acceleration is zero. Reason: Acceleration does not depend on force.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Assertion is incorrect but Reason is correct

Q. A car travels at a constant speed of $30\text{m/s}$ around a level circular bend of radius $100\text{m}$. What is the minimum coefficient of static friction between the tires and the road in order for the car to go round the bend without skidding?

1. $0.8$
2. $0.9$
3. $0.7$
4. $0.55$

Q. A car is travelling on a track which has radius of curvature $50\text{m}$. What is the maximum safe speed with which the car can travel on this track? Take $g=10{\text{m/s}}^2$. Assume coefficient of friction to be 0.8.

1. $10\sqrt{3}\text{m/s}$
2. $10\text{m/s}$
3. $20\text{m/s}$
4. $10\sqrt{5}\text{m/s}$

Q.

A particle of mass m rotates with a uniform angular speed $\omega$. It is viewed from a frame rotating about the Z-axis at a distance a from the particle, with a uniform angular speed ${\omega }_0$. The centrifugal force on the particle is

1. m${\omega }^2$a

2. m${\omega }_0^2$a

3. m $\omega {\omega }_{0}a$

4. m ${\left(\frac{\omega +{\omega }_0}{2}\right)}^2$ a

Q. locate the centre of mass of one quarter of risk of radius R.

Q. The minimum velocity (in m/s) with which a car driver must traverse a flat curve of radius 150 m and coefficient of friction 0.6 to avoid skidding is:

1. 60 m/s
2. 30 m/s
3. 15 m/s
4. 25 m/s

Q. A block of mass m is revolving under the action of contact forces and gravity on a smooth horizontal plane with cons†an t speed v. If the radius of the circular path is R, then net contact force on the block is (1) mv^2/R (2) mg (3) m \sqrt{v^4/R^2+g^2} (4) mg+ mv^2/R

Q. A car travelling on a level road with a curve of radius $32\text{m}$. The coefficient of static friction between the road and tyre of car is $0.2$. What speed will put the car on verge of sliding? $(g=10{\text{m/s}}^2)$

1. $6\text{m/s}$
2. $13\text{m/s}$
3. $8\text{m/s}$
4. $10\text{m/s}$

Q. In a children's park a heavy rod is pivoted at the centre and is made to rotate about the pivot so that the rod always remains horizontal. Two kids hold the rod near the ends and thus rotate with the rod as shown in figure. Let the mass of each kid be $15\text{kg}$, the distance between the points of the rod where the two kids hold it be $3.0\text{m}$ and suppose that the rod rotates at the rate of $20$ revolutions per minute. Find the force of friction exerted by the rod on one of the kids.

1. $80\text{N}$
2. $110\text{N}$
3. $100\text{N}$
4. $90\text{N}$

Q. A flat curve on a highway has a radius of curvature $400m$. A car goes around a curve at a speed of $32m/s$. What is the minimum value of coefficient of friction that will prevent the car from sliding? ($g=9.8m/s^2$)

Q. A $1200\text{kg}$ automobile rounds a level curve of radius $200\text{m}$, on an unbanked road with a velocity of $72\text{km/h}$. What is the minimum coefficient of static friction between the tyres and road in order that the automobile may not skid? $(g=10{\text{m/s}}^2)$

1. $0.15$
2. $0.2$
3. $0.3$
4. $0.4$