| 1. | \(0.5\) | 2. | \(0.75\) |
| 3. | \(0.25\) | 4. | \(0.40\) |
| 1. | \(50\) ms–2 | 2. | \(1.2\) ms–2 |
| 3. | \(150\) ms–2 | 4. | \(1.5\) ms–2 |
Calculate the acceleration of the block and trolly system shown in the figure. The coefficient of kinetic friction between the trolly and the surface is \(0.05.\)
( \(g=10~\text{m/s}^2,\) the mass of the string is negligible and no other friction exists)
| 1. | \( 1.25~\text{m/s}^2\) | 2. | \( 1.50~\text{m/s}^2\) |
| 3. | \(1.66~\text{m/s}^2\) | 4. | \( 1.00~\text{m/s}^2\) |
A body of mass \(m\) is kept on a rough horizontal surface (coefficient of friction = \(\mu).\) A horizontal force is applied to the body, but it does not move. The resultant of normal reaction and the frictional force acting on the object is given by \(\vec {F}\) where:
1. \(|{\vec {F}}| = mg+\mu mg\)
2. \(|\vec {F}| =\mu mg\)
3. \(|\vec {F}| \le mg\sqrt{1+\mu^2}\)
4. \(|\vec{F}| = mg\)
Which one of the following statements is incorrect?
| 1. | Rolling friction is smaller than sliding friction. |
| 2. | The limiting value of static friction is directly proportional to the normal reaction. |
| 3. | Frictional force opposes the relative motion. |
| 4. | The coefficient of sliding friction has dimensions of length. |
A plank with a box on it at one end is gradually raised about the other end. As the angle of inclination with the horizontal reaches \(30^\circ,\) the box starts to slip and slide \(4.0~\text m\) down the plank in \(4.0~\text s.\) The coefficients of static and kinetic friction between the box and the plank will be, respectively:
| 1. | \(0.6\) and \(0.6\) | 2. | \(0.6\) and \(0.5\) |
| 3. | \(0.5\) and \(0.6\) | 4. | \(0.4\) and \(0.3\) |
A block \(\mathrm{A}\) of mass \(m_1\) rests on a horizontal table. A light string connected to it passes over a frictionless pulley at the edge of the table and from its other end, another block \(\mathrm{B}\) of mass \(m_2\) is suspended. The coefficient of kinetic friction between block \(\mathrm{A}\) and the table is \(\mu_k\). When block \(\mathrm{A}\) is sliding on the table, the tension in the string is:
| 1. | \( \dfrac{\left({m}_2+\mu_{{k}}{m}_1\right) {g}}{\left({m}_1+{m}_2\right)}\) | 2. | \( \dfrac{\left({m}_2-\mu_{{k}} {m}_1\right) {g}}{\left({m}_1+{m}_2\right)}\) |
| 3. | \(\dfrac{{m}_1 {~m}_2\left(1-\mu_{{k}}\right) {g}}{\left({m}_1+{m}_2\right)}\) | 4. | \( \dfrac{{m}_1 {~m}_2\left(1+\mu_{{k}}\right)}{{m}_1+{m}_2} {g}\) |
A system consists of three masses \(m_1,\) \(m_2,\) and \(m_3\) connected by a string passing over a pulley \(\mathrm{P}.\) The mass \(m_1\) hangs freely, and \(m_2\) and \(m_3\) are on a rough horizontal table (the coefficient of friction \(=\mu.\)) The pulley is frictionless and of negligible mass. The downward acceleration of mass \(m_1\) is:
(Assume \(m_1=m_2=m_3=m\) and \(g\) is the acceleration due to gravity.)

| 1. | \(\dfrac{g(1-g \mu)}{9}\) | 2. | \(\dfrac{2 g \mu}{3}\) |
| 3. | \( \dfrac{g(1-2 \mu)}{3}\) | 4. | \(\dfrac{g(1-2 \mu)}{2}\) |