I dont need the work shown I just need the answers in the

10. A mass of 0.5 kg connected to a spring of force constant 40 Nm oscillates a frictionless surface. What is the total on a, 4500 energy of the system if the amplitude of the motion is b. 450 J c, 45 J d. 0.450 11. Mechanical energy is conserved if forces are conservative b, if forces are nonconservative c, work done depends on path d, none of the above 12. A 2-kg object is moving at 3 m/s. A 4-N force is applied in the direction of motion and then removed after the object has traveled an additional 5 m. The work done by this force is: A) 9 J B) 18 J C) 20 J D) 29 J 13. A 1-kg block is lifted vertically 1 m at constant speed by a boy. The work done by the boy is about: A) 1 ft B) 1 J C) 10 J D) 0.1 J 14. The work done by gravity during the descent of a projectile is: A) positive B) negative (C) zero 15. An object moving at constant velocity in an inertial frame must A) have a net force on it B) eventually stop due to gravity C) have no frictional force acting on it D) have zero net force acting on it 16. Which of the following quantities is NOT a vector? A) Mass B) Displacement C) Force D) Acceleration 17. A motionless 400-N steel ball is suspended by a light rope from the ceiling. The tension in the rope is: E) 560 N C) 0 N D) 200 N B) 800 N A) 400 N 18. Acceleration is always in the direction: B) of the initial velocity A) of the displacement D) of the net force C) of the final velocity 19. A force of Nis: D) 1kg x 1m ls B) 1kg x 1m/s A) 1 kg/s 20. Which of the following groups does NOT contain a scalar quantity? force A) velocity, force, energy B) displacement, acceleration, C) acceleration, speed, energy D) energy, force, distance

Solution

10.) For a spring mass system, at the time of maximum compression, as in when the mass is at one of the extremes the entire energy of the system is stored as the PE of the spring.

Hence the total energy = PE of the spring at maximum compression = 0.5 x 40 x 0.0225 = 0.45 J Hence Option D

11.) Mechanical energy is the sum of Potential and kinetic energy and remaines conserved only if the forces are conservative. Option A

12.) It needs to be understood that irrespective of the initial state of the body, the work done by a force F over a displacement S is given as W = F.S

As a force of 4 N acts over a distance of 5 m, the net work done by that particular force would 4 x 5 = 20 J

Hence Option C

13.) The boy while lifting the weight would be applying a force equal to the weight of the block and then displaces it by 1 m.

Therefore work = mgh which is approximately equal to 10J. Hence option C

14.) The gravity while descent of the projectile does positive work on it, This can be understood by the fact that the displacement of the projectile happens in the direction of the force applied by the gravity. Hence option A

15.) For the body to have no acceleration, that is, constant velocity, it must have no net force acting on it. Hence option D

16.) Mass is not a vector as it doesn\'t have a direction and is a physical property of a body. Hence option A

17.) As the steel ball is at rest, the net force acting on it must be zero, Hence the weight of the ball must be balanced by the tension in the wire. That is the tension on the wire = 400 N

18.) Acceleration is always in the direction of the net force. Option D

19.) Force 1 N is 1 Kg x 1m.s² Hence option C

20.) Option B. The quantities displacement acceleration and force, all three are vectors as they have a magnitude and a direction associated with them.