Let \(F,F_N\) and \(f\) denote the magnitudes of the contact force, normal force and the friction exerted by one surface on the other kept in contact. If none of these is zero,
(a) | \( F>F_N \) |
(b) | \( F>f \) |
(c) | \( F_N>f \) |
(d) | \( F_N-f<F<F_N+f\) |
Choose the correct option:
1. | (a), (b) and (c) |
2. | (a), (b) and (d) |
3. | (b), (c) and (d) |
4. | All of these |
The contact force exerted by a body A on another body B is equal to the normal force between the bodies. We conclude that
(a) the surfaces must be frictionless
(b) the force of friction between the bodies is zero
(c) the magnitude of normal force equals that of friction
(d) the bodies may be rough but they don’t slip on each other
Choose the correct option:
1. (a) and (b)
2. (b) and (c)
3. (b) and (d)
4. (a) and (c)
Mark the correct statements about the friction between two bodies.
(a) | static friction is always greater than kinetic friction. |
(b) | coefficient of static friction is always greater than the coefficient of kinetic friction. |
(c) | limiting friction is always greater than kinetic friction. |
(d) | limiting friction is never less than static friction. |
Choose the correct option:
1. | (a), (b) and (c) |
2. | (b), (c) and (d) |
3. | (a) and (d) |
4. | (c) and (d) |
A block is placed on a rough floor and a horizontal force \(F\) is applied on it. The force of friction \(f\) by the floor on the block is measured for different values of \(F\) and a graph is plotted between them.
(a) | \(45^{\circ}.\) | The graph is a straight line of slope
(b) | \(F\)-axis. | The graph is a straight line parallel to the
(c) | \(45^{\circ}\) for small \(F\) and a straight line parallel to the \(F\)-axis for large \(F.\) | The graph is a straight line of slope
(d) | There is a small kink on the graph. |
Choose the correct option:
1. (a) and (b)
2. (b) and (c)
3. (c) and (d)
4. (a) and (d)
Consider a vehicle going on a horizontal road towards the east. Neglect any force by the air. The frictional forces on the vehicle by the road
(a) is towards east if the vehicle is accelerating
(b) is zero if the vehicle is moving with a uniform velocity
(c) must be towards the east
(d) must be towards the west
Choose the correct option:
1. (a) and (b)
2. (a) and (c)
3. (b) and (c)
4. (c) and (d)
When a particle moves in a circle with a uniform speed
1. its velocity and acceleration are both constant
2. its velocity is constant but the acceleration changes
3. its acceleration is constant but the velocity changes
4. its velocity and acceleration both change
Two cars having masses m1 and m2 move in circles of radii r1 and r2 respectively. If they complete the circles in equal time, the ratio of their angular speeds ω1 / ω2 is
1. m1 / m2
2. r1 / r2
3. m1r1 / m2r2
4. 1
A car moves at a constant speed on a road as shown in the figure. The normal force by the road on the car is \(N_A\) and \(N_B\) when it is at the points \(A\) and \(B\) respectively.
1. | \( N_A=N_B \) |
2. | \( N_A>N_B \) |
3. | \(N_A<N_B\) |
4. | \(N_A\) and \(N_B\) | insufficient information to decide the relation of
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 \(v\). The centrifugal force on it is:
1. | \(\frac{mv^2}{r}\) towards the centre |
2. | \(\frac{mv^2}{r}\) away from the centre |
3. | \(\frac{mv^2}{r}\) along the tangent through the particle |
4. | zero |
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
1. \(\mathrm{m} \omega^{2} \mathrm{a}\)
2. \(\mathrm{m} \omega_{0}^{2} \mathrm{a}\)
3. \(\left(\frac{\omega+\omega_{0}}{2}\right)^{2} \mathrm{a}\)
4. \(\mathrm{m} \omega ~\omega_{0} \mathrm{a}\)