You are driving a motorcycle on a horizontal road. It is moving with a uniform velocity. Is it possible to accelerate the motorcycle

without putting higher petrol input rate into the engine?

Some washing machines have cloth driers. It contains a drum in which wet clothes are kept. As the drum rotates, the water particles get separated from the cloth. The general description of this action is that “the centrifugal force throws the water particles away from the drum”. Comment on this statement from the viewpoint of an observer rotating with the drum and the observer who is washing the clothes.

A small coin is placed on a record rotating at rev/minute. The coin does not slip on the record. Where does it get the required centripetal force from?

A bird while flying takes a left turn, where does it get the centripetal force from?

Is it necessary to express all angles in radian while using the equation ω = ω₀ + αt?

After a good meal at a party you wash your hands and find that you have forgotten to bring your handkerchief. You shake your hands vigorously to remove the water as much as you can. Why is water removed in this process?

A smooth block loosely fits in a circular tube placed on a horizontal surface. The block moves in a uniform circular motion along the tube as shown in figure below. Which wall (inner or outer) will exert a non-zero normal contact force on the block?

Consider the circular motion of the earth around the sun. Which of the following statements is more appropriate?

(a) Gravitational attraction of the sun on the earth is equal to the centripetal force.

(b) Gravitational attraction of the sun on the earth is the centripetal force.

A car driver going at some speed u suddenly finds a wide wall at a distance r. Should he apply brakes or turn the car in a circle of radius r to avoid collapsing with the wall.

A heavy mass m is hanging from a string in equilibrium without breaking it. When this same mass is set into oscillation the string breaks. Explain.

When a particle moves in a circle with a uniform speed

Two cars having masses m₁ and m₂ move in circles of radii r₁ and r₂ respectively. If they complete the circle in equal time, the ratio of their angular speeds ω₁/ω₂ is

A car moves at a constant speed on a road as shown in figure below the normal force by the road on the car is NA and N9 when it is at the points A and B respectively.

A particle of mass m is observed from an inertial frame of reference and is found to move in a circle of radius r with a uniform

speed u. The centrifugal force on it is

A particle of mass m rotates with a uniform angular speed ω. It is viewed from a frame rotating about the Z-axis with a uniform

angular speed ω₀. The centrifugal force on the particle is

A particle is kept fixed on a turntable rotating uniformly. As seen from the ground the particle goes in a circle, its speed is 20 cm/s and acceleration is 20 cm/s². The particle is now shifted to a new position to make the radius half of the original value. The new values of the speed and acceleration will be

Water in a bucket is whirled in a vertical circle with a string attached to it. The water does not fall down even when the bucket is inverted at the top of its path. We conclude that in this position

A stone of mass m tied to a string of length I is rotated in a circle with the other end of the string as the center. The speed of the stone is u. If the string breaks, the stone will move

A corn placed on a rotating turntable just slips if it is placed at a distance of 4 cm from the center. If the angular velocity of the

turntable is doubled, it will just slip at a distance of

A motorcycle is going on an over bridge of radius R. The driver maintains a constant speed. As the motorcycle is ascending on the over bridge, the normal force on it

Three identical cars A, B and C are moving at the same speed on three bridges. The car A goes on a plane bridge, B on a bridge convex upward and C goes on a bridge concave upward. Let F_A, F_B and F_C be the normal forces exerted by the cars on the bridges when they are at the middle of bridges.

A train A runs from east to west and another train B of the same mass runs from west to east at the same speed along the equator. A press the track with a force F₁ and B presses the track with a force F₂.

If the earth stops rotating, the apparent value of g on its surface will

A rod of length L is pivoted at one end and is rotated with a uniform angular velocity in a horizontal plane. Let T₁ and T₂ be the

tensions at the points L/₄ and 3L/4 away from the pivoted ends.

A simple pendulum having a bob of mass m is suspended from the ceiling of a car used in a stunt film shooting. The car moves up along an inclined cliff at a speed υ and makes a jump to leave the cliff and lands at some distance, Let R be the maximum height of the car from the top of the cliff. The tension in the string when the car is in air is

Let θ denote the angular displacement of a simple pendulum oscillating in a vertical plane. If the mass of the bob is m, the tension in the string is mg cosθ

An object follows a curved path. The following quantities may remain constant during the motion

Assume that the earth goes round the sun in a circular orbit with a constant speed of 30 km/s.

The position vector of a particle in a circular motion about the origin sweeps out equal area in equal time.

A particle is going in a spiral path as shown in figure (7.Q3) with constant speed.

A car of mass M is moving on a horizontal circular path of radius r. At an instant its speed is υ and is increasing at a rate a.

A circular road of radius r is banked for a speed υ = 40 km/hr. A car of mass m attempts to go on the circular road. The friction coefficient between the tyre and the road is negligible.

A person applies a constant force on a particle of mass m and finds that the particle moves in a circle of radius r with a uniform speed u as seen from an inertial frame of reference.

Find the acceleration of the moon with respect to the earth from the following data: Distance between the earth and the moon = 385 × 10 km and the time taken by the moon to complete one revolution around the earth = 273 days.

Find the acceleration of a particle placed on the surface of the earth at the equator due to earth’s rotation. The diameter of earth = 12800 km and it takes 24 hours for the earth to complete one revolution about its axis.

A particle moves in a circle of radius 1.0 cm at a speed given by u = 2.0 t where u is in cm/s and t in seconds. (a) Find the radial acceleration of the particle at t 1 s. (b) Find the tangential acceleration at t = 1 s. (c) Find the magnitude of the acceleration at t = 1 s.

(b) 2.0 cm/s²

(c)

A scooter weighing 150 kg together with its rider moving at 36 km/hr is to take a turn of radius 30 m. What horizontal force on the scooter is needed to make the turn possible?

If the horizontal force needed for the turn in the previous problem is to be supplied by the normal force by the road, what should be the proper angle of banking?

A park has a radius of 10 m. If a vehicle goes round it at an average speed of 18 km/hr, what should be the proper angle of banking?

If the road of the previous problem is horizontal (no banking), what should be the minimum friction coefficient so that a scooter going at 18 km/hr does not skid?

A circular road of radius 50 m has the angle of banking equal to 30⁰. At what speed should a vehicle go on this road 80 that the friction is not used?

In the Bohr model of hydrogen atom, the electron is treated as a particle going in a circle with the centre at the proton. The proton itself is assumed to be fixed in an inertial frame. The centripetal force is provided by the Coulomb attraction. In the ground state, the electron goes round the proton in a circle of radius 5.3 × 10^-11 m. Find the speed of the electron in the ground state. Mass of the electron = 9.1 × 10^-31 kg and charge of the electron = 1.6 × 10^-19 C.

A stone is fastened to one end of a string and is whirled in a vertical circle of radius R. Find the minimum speed the stone can have at the highest point of the circle.

A ceiling fan has a diameter (of the circle through the outer edges of the three blades) of 120 cm and rpm 1500 at full speed. Consider a particle of mass 1 g sticking at the outer end of a blade. How much force does it experience when the fan runs at full speed? Who exerts this force on the particle? How much force does the particle exert on the blade along its surface?

A mosquito is sitting on an L.P. record disc rotating on a turn table at revolutions per minute. The distance of the mosquito from the center of the turn table is lo cm. Show that the friction coefficient between the record and the mosquito is greater than it π²/81. Take g= 10 m/s².

A simple pendulum is suspended from the ceiling of a car taking a turn of radius 10 m at a speed of 36 km/h. Find the angle made by the string of the pendulum with the vertical if this angle does not change during the turn. Take g = 10 m/s².

The bob of a simple pendulum of length 1 m has mass loo g and a speed of 1.4 m/s at the lowest point in its path. Find the tension in the string at this instant.

Suppose the bob of the previous problem has a speed of 1.4 m/s when the string makes an angle of 0.20 radian with the vertical. Find the tension at this instant. You can use ≈ cosθ ≈ 1 - θ²/2 and sinθ ≈ θ, for small θ.

Suppose the amplitude of a simple pendulum having a bob of mass m is θ₀. Find the tension in the string when the bob is at its extreme position.

A person stands on a spring balance at the equator. (a) By what fraction is the balance reading less than his true weight? (b) If the speed of earth’s rotation is increased by such an amount that the balance reading is half the true weight, what will be the length of the day in this case?

A turn of radius 20 in is banked for the vehicles going at a speed of 36 km/h. If the coefficient of static friction between the road and the tyre is 0.4, what are the possible speeds of a vehicle so that it neither slips down nor skids up?

A motorcycle has to move with a constant speed on an over-bridge which is in the form of a circular arc of radius R and has a total length L. Suppose the motorcycle starts from the highest point. (a) What can its maximum velocity be for which the contact with the road is not broken at the highest point? (b) If the motorcycle goes at speed 1/√2 times the maximum found in part (a), where will it lose the contact with the road? (c) What maximum uniform speed can it maintain on the bridge if it does not lose contact anywhere on the bridge?

A car goes on a horizontal circular road of radius R, the speed increasing at a constant rate The friction coefficient between the road and the tyre is μ. Find the speed at which the car will skid.

A block of mass m is kept on a horizontal ruler. The friction coefficient between the ruler and the block is μ. The ruler is fixed at one end and the block is at a distance L from the fixed end. The ruler is rotated about the fixed end in the horizontal plane through the fixed end. (a) What can the maximum angular speed be for which the block does not slip? (b) If the angular speed of the ruler is uniformly increased from zero at an angular acceleration a, at what angular speed will the block slip?

A track consists of two circular parts ABC and CDE of equal radius 100 m and joined smoothly as shown in figure (7-E1). Each part subtends a right angle at its center. A cycle weighing 100 kg together with the rider travels at a constant speed of 18 km/h on the track. (a) Find the normal contact force by the road on the cycle when it is at B and at D. (b) Find the force of friction exerted by the track on the Lyres when the cycle is at B, C and D. (c) Find the normal force between the road and the cycle just before and just after the cycle crosses C. (d) What should be the minimum friction coefficient between the road and the tyre, which will ensure that the cyclist can move with constant speed? Take g = 10 m/s².

In a children’s park a heavy rod is pivoted at the center 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 (figure 7-E2). Let the mass of each kid be 15 kg, the distance between the points of the rod where the two kids hold it be 30 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.

A hemispherical bowl of radius R is rotated about its axis of symmetry which is kept vertical. A small block is kept in the bowl at a position where the radius makes an angle θ with the vertical. The block rotates with the bowl without any slipping. The friction coefficient between the block and the bowl surface is μ, Find the range of the angular speed for which the block will not slip.

A particle is projected with a speed u at an angle θ with the horizontal. Consider a small part of its path near the highest position and take it approximately to be a circular arc. What is the radius of this circle? This radius is called the radius of curvature of the curve at the point.

What is the radius of curvature of the parabola traced out by the projectile in the previous problem at a point where the particle velocity makes an angle θ/2 with the horizontal?

A block of mass m moves on a horizontal circle against the wall of a cylindrical room of radius R. The floor of the room on which the block moves is smooth but the friction coefficient between the wall and the block is μ. The block is given an initial speed u₀. As a function of the speed u write (a) the normal force by the wall on the block, (b) the frictional force by the wall and (c) the tangential acceleration of the block. (d) Integrate the tangential acceleration to obtain the speed of the block after one revolution.

A table with smooth horizontal surface is fixed in a cabin that rotates with a uniform angular velocity ω in a circular path of radius R (figure 7-E3). A smooth groove AB of length L (<< R) is made on the surface of the table. The groove makes an angle θ with the radius OA of the circle in which the cabin rotates. A small particle is kept at the point A in the groove and is released to move along AB. Find the time taken by the particle to reach the point B.

A car moving at a speed of 36 km/hr is taking a turn on a circular road of radius 50 m. A small wooden plate is kept on the seat with its plane perpendicular to the radius of the circular road (figure 7-E4). A small block of mass loo g is kept on the seat which rests against the plate. The friction coefficient between the block and the plate is μ = 058. (a) Find the normal contact force exerted by the plate on the block. (b) The plate is slowly turned so that the angle between the normal to the plate and the radius of the road slowly increases. Find the angle at which the block will just start sliding on the plate.

A table with smooth horizontal surface is placed in a cabin which moves in a circle of a large radius R (figure 7-E5). A smooth pulley of small radius is fastened to the table. Two masses m and 2m placed on the table are connected through a string going over the pulley. Initially the masses are held by a person with the strings along the outward radius and then the system is released from rest (with respect to the cabin). Find the magnitude of the initial acceleration of the masses as seen from the cabin and the tension in the string.