1. Define the term centre of gravity of an object. (1mk)
Refers to the point where the whole weight of a body acts from
2. Differentiate between a body
... [Show More] in a stable state of equilibrium and one in an
unstable state of equilibrium.
A body is said to be in stable state of equilibrium if it returns to its original
position after being displaced slightly, while a body is said to be in an
unstable state of equilibrium if on being displaced slightly does not return to
its original position
3. With the aid of a diagram, describe an experiment to determine the cog of
an irregular lamina. (6mks)
Set the apparatus as shown below,
- Remove the cardboard and balance it on the tip of a pencil.
- The suspended object will always rest with its centre of gravity vertically below its point of
support.
- The object balances on the tip of the pencil it placed at its centre of gravity.
4. Use simple sketches to show the three states of equilibrium. (3mks)
Stable state
Unstable state
Neutral state
5. State two ways in which the stability of an object can be reduced. (2mk)
-Increasing the height of the object/position of C.OG
-Reducing the base area of the object
6. Explain why racing cars have wide tyres. 1mk
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Wider tires increase the base area of the race cars which in turn
lowers the centre of gravity hence increase stability.
This allows the rally cars to move around corners at relatively higher
speeds without overturning.
7. State two factors that determine the stability of a vehicle
- height of the vehicle/position of C.O.G
- base area the vehicle is resting on
8. A bus carrying standing passengers has a higher chance of overturning than
one with sitting passengers. Explain. (1mk)
Standing passengers each raise the center of gravity of the given bus thus
making it unstable thus susceptible to overturning
9. The stability of a body can be increased by increasing the base area and
lowering its centre of gravity. State one way of lowering its centre of
gravity.
- reducing the height of the given body
- Having more weight on the lower part of the body.
10. A person carrying a heavy luggage using one hand leans away from the
luggage. State the reason for this. (1mk)
-He/she leans in the opposite side in order to adjust the position of his
centre of gravity until a state of balance is achieved.
11. State the necessary conditions for equilibrium of body which is acted upon
by a number of forces
-The sum of clockwise moments about any point is equal to the sum of
anticlockwise moments about the same point.
-The sum of forces in one direction on a body is equal to the sum of forces
acting on the body in the opposite direction.
12. State the modification introduced in the modern buses so as to enhance
stability
- The heaviest parts (engine, luggage compartments) are located at the
lower most end of the bus.
-The uppermost parts of the busses are made of lighter materials.
13. Tall buildings are built with lighter materials at the upper part. Explain.(2mk
This is to reduce weight exerted at the top of the building, thus ensures the
center of gravity of the building is low thus the building becomes stable.
14. A tight rope walker carries a pole to maintain stability. Explain how he used
it to achieve it.
The pole adds more weight below the center of gravity of the walker, hence
increased stability
15. State two factors that may be considered when designing the body of a
racing car to enhance stability. (2mk)
-Height of the car.
-base area of the car
16. State two conditions necessary for a rigid body to be in equilibrium. (2mk)
-Should have a lower centre of gravity
-Should have wider base area.
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17. The figure below shows a uniform cardboard in the shape of a parallelogram.
Locate the centre of gravity of the cardboard. (1mk)
18. The diagram below shows a L – shaped solid Identify the position of centre of
gravity. (2mks)
19. Locate the centre of gravity of the figure below. (3mk)
20. Figure below shows a marble placed on an inverted bowl.
State and explain the type of equilibrium the marble is in. (2 mk)
-Unstable state; position of the cog shifts when the ball is slightly displaced [Show Less]