If a vector 2ˆi+3ˆj+8ˆk is perpendicular to the vector −4ˆi+4ˆj+αˆk, then the value of α will be:
1. −1
2. −12
3. 12
4. 1
A block of 1 kg is released from the top of a smooth curve AB, and then it encounters a rough surface BC, coming to rest at C. The work done by friction is:
(take g=10 m/s2)
1. | 25 J | 2. | 50 J |
3. | −25 J | 4. | −50 J |
The work done by all the forces (external and internal) on a system equals the change in:
1. total energy
2. kinetic energy
3. potential energy
4. none of these
1. | 30 cm | 2. | 27 cm |
3. | 24 cm | 4. | 28 cm |
A body of mass 1 kg is thrown upwards with a velocity 20 ms-1. It momentarily comes to rest after attaining a height of 18 m. How much energy is lost due to air friction?
(Take g=10 ms-2)
1. 20 J
2. 30 J
3. 40 J
4. 10 J
A bicyclist comes to a skidding stop in 10 m. During this process, the force on the bicycle due to the road is 200 N is directly opposed to the motion. The work done by the cycle on the road is:
1. +2000 J
2. −200 J
3. zero
4. −20000 J
1. | zero | 2. | −12mu2cos2θ |
3. | −12mu2sin2θ | 4. | −12mu2 |
A body of mass 0.5 kg travels in a straight line with velocity v=ax3/2 where a=5 m−1/2s−1. The work done by the net force during its displacement from x=0 m to x=2 m is:
1. 15 J
2. 50 J
3. 10 J
4. 100 J