Deck 4: Dynamics, and Energy

Question 1

Decide whether each of these statements is True (T) or False
For a spring, which obeys Hooke's law, when it is stretched to give an extension of x:
(i) The work done in giving this extension is Fx
(ii) The work done in giving this extension is the product of the stress and strain.

A) (i) T (ii) T
B) (i) T (ii) F
C) (i) F (ii) T
D) (i) F (ii) F

Answer 1

D

Question 2

Decide whether each of these statements is True (T) or False
In the absence of and dissipation of mechanical energy, when an object falls from some height to the
Ground:
(i) The sum of the kinetic and potential energies will remain constant during the falling.
(ii) The kinetic energy will be a maximum just before the object hits the ground.

A) (i) T (ii) T
B) (i) T (ii) F
C) (i) F (ii) T
D) (i) F (ii) F

Answer 2

A

Question 3

A flywheel is kept rotating at a constant 4 rev/s by a constant torque of 20 N m. The power input to the flywheel is:

A) 80 J
B) B 80π J
C) C 160π J
D) D 320π J

Answer 3

C

Question 4

An object of mass 2 kg rests on a smooth plane inclined at an angle of 30º to the horizontal. Take the acceleration due to gravity as g. The reaction force at right angles to the plane will be:

A) 0.87g N
B) 1g N
C) 1.73g N
D) 2g N

Question 5

An object of mass 2 kg rests on a smooth plane inclined at an angle of 30º to the horizontal. Take the acceleration due to gravity as g. The component of the weight acting down and parallel to the plane will be:

A) 0.87g N
B) 1g N
C) 1.73g N
D) 2g N

Question 6

Decide whether each of these statements is True (T) or False
A hammer of mass 2 kg is moving with a velocity of 4 m/s when it hits a nail. If it comes to rest in 0.1 s:
(i) The momentum of the hammer before hitting the nail is 8 kg m/s.
(ii) The force acting on the nail when hit by the hammer is 8 N.

A) (i) T (ii) T
B) (i) T (ii) F
C) (i) F (ii) T
D) (i) F (ii) F