State the energy changes in the following devices while in use:
i) A loud speaker
ii) A glowing electric bulb
A man having a box on his head, climbs up a slope and another man having an identical box walks the same distance on a levelled road.? What does more work against the force of gravity and why?
A body is thrown vertically upwards. Its velocity keeps on decreasing. What happens to its kinetic energy as its velocity becomes zero.
Two forces each of 5 N act vertically upwards and downwards respectively on the the two ends of a uniform metre rule which is placed at its mid-point as shown in the diagram. Determine the magnitude of the resultant moment of these forces about the mid-point?
Given,
F1 = F2 = 5 N
D1 = d2 = 0.5 m
Torque, τ = F × d
τ1 = F1 × d1 = 5 N × 0.5 m
= 2.5 Nm, in the anti-clockwise direction.
τ2 = F2 × d2 = 5 N × 0.5 m
= 2.5 Nm , in the anticlockwise direction
The resultant moment of force = τ1 + τ2
= 2.5 + 2.5 = 5 N m , in anti-clockwise direction.
Draw a diagram to show how a single pulley can be used so as to have its ideal M.A. = 2
Derive a relationship between mechanical advantages, velocity ratio and efficiency of a machine.