General
✓✗The maximum value of static friction is proportional to
- the area of contact
- the volume of the body
- the speed of the body
- the normal reaction
General
✓✗A 1 kg block rests on a 2 kg plank lying on a smooth floor; the coefficient of friction between block and plank is 0.3. The plank is pulled horizontally with 15 N. The acceleration of the plank is (g = 10 m s−2)
- 3 m s−2
- 6 m s−2
- 7.5 m s−2
- 5 m s−2
General
✓✗The velocity of a 0.5 kg particle varies with its position as \( v = \alpha\sqrt{x} \), where α = 4 m1/2 s−1. The force on the particle is
- 4 N, increasing with x
- 8 N, constant
- 2 N, constant
- 4 N, constant
General
✓✗A stationary nucleus of mass 238 u emits an alpha particle (4 u) with speed v. The recoil speed of the remaining nucleus is
- v
- \( \dfrac{4v}{234} \)
- \( \dfrac{234v}{4} \)
- \( \dfrac{4v}{238} \)
General
✓✗A block of mass 2 kg on a rough incline of 30° is just about to slide down. The coefficient of static friction is increased slightly. The friction force on the block now
- becomes zero
- increases
- stays 10 N
- decreases
General
✓✗A lift of mass 500 kg carries 300 kg of passengers. If the maximum tension the cable can bear is 12000 N, the maximum upward acceleration is (g = 10 m s−2)
- 2.5 m s−2
- 10 m s−2
- 15 m s−2
- 5 m s−2
General
✓✗A particle is in equilibrium under the action of several concurrent forces. Then
- the vector sum of the forces is zero
- the forces must be equal in magnitude
- the forces must all be parallel
- each force must be zero
General
✓✗A lift of mass 1000 kg is moving with an upward acceleration of 1 m s−2. The tension developed in the cable supporting the lift is (take g = 9.8 m s−2)
- 11000 N
- 10000 N
- 10800 N
- 9800 N
General
✓✗A 2 kg block on a smooth table is connected by a string over a smooth pulley at the edge to a hanging 3 kg block. The tension in the string is (g = 10 m s−2)
- 30 N
- 18 N
- 6 N
- 12 N
General
✓✗A string over a fixed pulley connects masses m and 3m. The force on the pulley support (pulley and string light) when they move is
- 6mg
- 4mg
- 2mg
- 3mg
General
✓✗A block of mass 1 kg is placed on the horizontal floor of a truck (coefficient of static friction μ = 0.6). The truck is moving with an acceleration of 5 m s−2. The frictional force on the block is (take g = 9.8 m s−2)
- 6 N
- 5 N
- 8 N
- 5.88 N
General
✓✗A satellite in force-free space sweeps up stationary interplanetary dust at a rate dM/dt = αv, where M is the mass and v the speed of the satellite and α is a constant. The acceleration of the satellite is
- \( -\alpha v^2 \)
- \( -\dfrac{\alpha v^2}{M} \)
- \( -\dfrac{2\alpha v^2}{M} \)
- \( -\dfrac{\alpha v^2}{2M} \)
General
✓✗Three forces acting on a particle keep it in equilibrium. These forces can be represented by
- three sides of a square
- the three sides of a triangle taken in order
- three parallel lines
- the diagonals of a parallelogram
General
✓✗A bus starts from rest with a uniform acceleration. A box on the floor (μs = 0.2) does not slide. The maximum acceleration of the bus for this, and the friction on a 20 kg box at that acceleration, are (g = 10 m s−2)
- 2 m s−2 and 20 N
- 20 m s−2 and 40 N
- 2 m s−2 and 40 N
- 0.2 m s−2 and 4 N
General
✓✗A gramophone record is revolving with an angular velocity ω. A coin is placed at a distance r from the centre of the record. The coefficient of static friction is μ. The coin will revolve with the record if
- \( r \le \dfrac{\mu g}{\omega^2} \)
- \( r < \dfrac{\omega^2}{\mu g} \)
- \( r = \mu g\,\omega^2 \)
- \( r \ge \dfrac{\mu g}{\omega^2} \)