4. Forces Flashcards
State the conditions necessary for a body to be in equilibrium.
Resultant force acting on the body in any direction is zero, and resultant moment on the body about any axis is zero.
Explain what is meant by the centre of gravity of an object.
The centre of gravity of a body is the point at which the entire weight of the body appears to act.
Explain why some slopes cannot be made anymore steeper than they already are.
Speed of the object increases gradually.
A string is used to lift an iron sphere vertically upwards from a beaker of liquid, explain why the string breaks.
When the sphere is lifted out of the liquid, the volume of liquid displaced is reduced. This causes upthrust acting on the sphere to decrease. To maintain equilibrium, tension of the string increases and the string breaks when maximum tension of the string is exceeded.
Define upthrust.
Upthrust is the upward force exerted by a fluid on a submerged or floating object. It arises due to the difference in pressure between the upper and lower surfaces of the object.
Define Hooke’s Law.
Hooke’s Law states that extension or compression in a material is directly proportional to the applied force, provided that the limit of proportionality is not exceeded.
