(a) Work, Energy and Power - Jamb Physics Past Questions and Answers

Question 31:

• JAMB 2000

If the force and the velocity on a system are each reduced simultaneously by half, the power of the system is

A. Doubled
B. Reduced to a quarter
C. Reduced by half
D. Constant

Question 32:

• JAMB 2001

A stone of mass 1kg is dropped from a height of 10m above the ground and falls freely under gravity. Its kinetic energy 5m above the ground is then equal to

A. Its kinetic energy on the ground
B. Twice its initial potential energy
C. Its initial potential energy
D. Half its initial potential energy

Question 33:

• JAMB 2001

A gas with initial volume of 2 X 10^-6m³ is allowed to expand to six times its initial value at constant pressure of 2 x 10⁵Nm^-2. The work done is

A. 2.0J
B. 4. 0 J
C. 12.0 J
D. 2.4 J

Question 34:

• JAMB 2001

A working electric motor takes a current of 1.5 A when the p.d across it is 250V. If its efficiency is 80%, the power output is

A. 300.0W
B. 469.0W
C. 133.0W
D. 4.8W

Question 35:

• JAMB 2002

The diagram above shows the force (F) acting on an object through a distance (x). The work done on this object is expressed as

A. Fx J
B. ^Fx/₂ J
C. Fx² J
D. ^F/_x J