Question

13. The work done by a force F which causes on an ob- ject a displacement d'is minimum when the angle between the force and the displacement is: (a) O deg (b) 20 deg (c) 90 deg (d) none of the above 14. On the ballistic pendulum experiment, we cal- culate the speed of the projectile by applying two conservation principles: (a) heat and total energy (b) linear and angular momenta (c) angular momentum, and mechanical energy (d) linear momentum, and mechanical energy 15. A particle has an initial kinetic energy K; = 300J and after applying a pushing force, the kinetic en- ergy is Ky = 800J. The work done by the force on the particle is (a) 1.53 (b) 500J (c) 100J (d) 60000J 16. A spaceship's main engine produces 3000N of thrust. If the spaceship's mass is 30000kg, for how much time the engine has to be fired in order to increase the spaceship's speed by Im/s? (a) 500 (b) 1005 (c) 10s (d) none of the above

Answer 1