(i) Volume = $\frac{mass}{density}$ = $\frac{20}{800}$ = 0.025 m3
(ii) Volume of water = volume of log = 0.025 m3
Upthrust = 0.025 x 1000 x 10 = 250 N
(iii) Tension + weight = upthrust Tension = 250 - 200 = 50
johnmulu answered the question on June 5, 2017 at 08:28
- Figure 12 shows a weighing balance on which a beaker containing some water is placed. The reading on the balance is 2.80 N. A metal block weighing 2.7 N is suspended from a spring balance. (Solved)
Figure 12 shows a weighing balance on which a beaker containing some water is placed. The reading on the balance is 2.80 N. A metal block weighing 2.7 N is suspended from a spring balance.
(i) State what is observed on the spring balance and the weighing balance, as the metal block is gradually lowered into the water.
(I) Observation on spring balance.
(II) Observation on weighing balance
(ii) Explain the observation made on the spring balance in (I).
Date posted: June 5, 2017. Answers (1)
- Figure 13 shows a log of wood of mass 20 kg submerged in water in a pond and held in position by a string fixed to the bottom of the pond. (Solved)
Figure 13 shows a log of wood of mass 20 kg submerged in water in a pond and held in position by a string fixed to the bottom of the pond.
Given that the density of water is 1000 kgm -3 and that of wood is 800 kgm -3, determine the;
(i) Volume of the log.
(ii) Upthrust of the log.
(iii) Tension in the string.
Date posted: June 5, 2017. Answers (1)
- Figure 18 shows parts of a simple submarine, a ship that can travel both on water and under water. To do this water is pumped in or out of the ballast tanks. (Solved)
Figure 18 shows parts of a simple submarine, a ship that can travel both on water and under water. To do this water is pumped in or out of the ballast tanks.
Explain how the tanks are used to change the depth of the submarine.
Date posted: June 5, 2017. Answers (1)
- Figure 8 shows a stone of mass 4.0 kg increased in water and suspended from a spring balance(Solved)
Figure 8 shows a stone of mass 4.0 kg increased in water and suspended from a spring balance with a string. The beaker was placed on a compression balance whose reading was 85 N. The density of the stone was 3000 kgm-3 while the density of the liquid was 800 kgm -3.
Determine the;
(a) volume of the liquid displaced;
(b) upthrust on the stone;
(c) Reading of the spring balance;
Date posted: June 5, 2017. Answers (1)
- Figure 10 shows a rectangular metal block of density 10500 kgm-3(Solved)
Figure 10 shows a rectangular metal block of density 10500 kgm-3 and dimensions 30 cm x 20 cm x 20 cm suspended inside a liquid of density 1200 kgm-3 by a string attached to a point above the liquid. The three forces acting on the block are the tension T, On the string, the weight W, of the block and the upthrust, U due to the liquid.
(i) Write the expression relating T, W and U when the block is in equilibrium inside the liquid.
(ii) Determine the weight, W of the block.
(iii) Determine the weight of the liquid displaced by the fully submerged block.
(iv) Hence determine the tension, T in the string.
Date posted: June 5, 2017. Answers (1)
- The system in Figure below is in equilibrium. (Solved)
The system in Figure below is in equilibrium.
When temperature of the water is raised the system is observed to tilt to the right. State the reason for this observation.
Date posted: June 5, 2017. Answers (1)
- Figure 14 shows a cork floating on water and held to the bottom of the beaker by a thin thread. (Solved)
Figure 14 shows a cork floating on water and held to the bottom of the beaker by a thin thread.
(i) Name the forces acting on the cork
(ii) Describe how each of the forces mentioned in (i) above changes when water is added into the beaker until it fills up.
Date posted: June 5, 2017. Answers (1)
- Figure 13 shows a simple hydrometer. (Solved)
Figure 13 shows a simple hydrometer.
(i) State the purpose of the lead shots in the glass bulb.
(ii) How would the hydrometer be made more sensitive?
(iii) Describe how the hydrometer is calibrated to measure relative density.
Date posted: June 5, 2017. Answers (1)
- The uniform bar in figure 7 is pivoted at its midpoint. It is in equilibrium under the action of two identical balloons filled with equal volumes of different light gases at the same temperature. (Solved)
The uniform bar in figure 7 is pivoted at its midpoint. It is in equilibrium under the action of two identical balloons filled with equal volumes of different light gases at the same temperature.
Explain why the bar may not remain equilibrium if the temperature of the surrounding changes.
Date posted: June 5, 2017. Answers (1)
- In an experiment to determine the density of a liquid, a uniform metal cylinder of cross-sectional area 6.2 cm2 and length 4.5 cm was hang...(Solved)
In an experiment to determine the density of a liquid, a uniform metal cylinder of cross-sectional area 6.2 cm2 and length 4.5 cm was hang from a spring balance and lowered gradually into the liquid. The upthrust was determined for various submerged lengths. The results obtained are shown on the graph in figure 1.
Using the graph, determine:
(i) The value of the upthrust when the cylinder is fully submerged.
(ii) The density of the liquid.
Date posted: June 5, 2017. Answers (1)
- The system in Figure 2 is in equilibrium at room temperature. The system is taken outside where the temperature is 10oC higher for some time. (Solved)
The system in Figure 2 is in equilibrium at room temperature. The system is taken outside where the temperature is 10oC higher for some time.
Explain why it tips to right immediately it is returned to the room.
Date posted: June 2, 2017. Answers (1)
- Figure 19 shows two spheres made of wax each of mass 0.10 kg held in a liquid by strings A and B. (Solved)
Figure 19 shows two spheres made of wax each of mass 0.10 kg held in a liquid by strings A and B.
If the upthrust on each sphere is 1.05 N, determine the tension in each string. (acceleration due to gravity g = 10ms-2)
Date posted: June 2, 2017. Answers (1)
- Figure 2 shows a uniform bar in equilibrium. (Solved)
Figure 2 shows a uniform bar in equilibrium.
When water is added into the beakers A and B until the weights are submerged, it is observed that the bar tips towards B. Explain this observation.
Date posted: June 2, 2017. Answers (1)
- Figure 7 represents a block of uniform cross sectional area of 6.0 cm2 floating on two liquids A and B. The lengths of the block in each liquid are as shown. (Solved)
Figure 7 represents a block of uniform cross sectional area of 6.0 cm2 floating on two liquids A and B. The lengths of the block in each liquid are as shown.
Give that the density of liquid A is 800 kgm-3 and that of liquid B is 1000 kgm-3, determine the:
(i) Weight of liquid A displaced
(ii) Weight of liquid B displaced.
Date posted: June 2, 2017. Answers (1)
- Figure 13 shows a pendulum bob suspended by a thread moving in a horizontal circle. (Solved)
Figure 13 shows a pendulum bob suspended by a thread moving in a horizontal circle.
(i) Name two forces acting on the pendulum bob as it moves.
(ii) State what happens to each of the forces when the angular velocity of the pendulum bob is increased.
(iii) State two applications of uniform circular motion in daily life.
Date posted: June 2, 2017. Answers (1)
- Figure 7 shows an object at the end of a light spring balance connected to a peg using a string. The object is moving in a circular path on a smooth horizontal table with a constant speed. (Solved)
Figure 7 shows an object at the end of a light spring balance connected to a peg using a string. The object is moving in a circular path on a smooth horizontal table with a constant speed.
(i) State the purpose of banking roads at bends.
(ii) State a reason why the object is accelerating while its speed remains constant.
(iii) Give that the mass of the object is 0.5 kg and it is moving at a speed of 8 ms-1 at a radius of 2m, determine the reading on the spring balance.
Date posted: June 2, 2017. Answers (1)
- Figure 10 shows the path of an object of mass m attached to a string of length r when whirled in a vertical circle at a constant speed V. A is the highest point on its path.(Solved)
Figure 10 shows the path of an object of mass m attached to a string of length r when whirled in a vertical circle at a constant speed V. A is the highest point on its path.
State the forces that provide the centripetal force on the object when it is at point A.
Date posted: June 2, 2017. Answers (1)
- Figure 11 shows a stone attached to the end of a string moving in a horizontal circle with a uniform speed of 2 ms-1. When the stone reaches point X on the circle, the string breaks
(Solved)
Figure 11 shows a stone attached to the end of a string moving in a horizontal circle with a uniform speed of 2 ms-1. When the stone reaches point X on the circle, the string breaks
State the magnitude of the velocity after the string breaks. and give a reason
Date posted: June 2, 2017. Answers (1)
- Three masses are placed on a rotating table at distances 6 cm, 9 cm and 12 cm respectively (Solved)
Three masses are placed on a rotating table at distances 6 cm, 9 cm and 12 cm respectively from the centre of rotation. When the frequency of rotation is varied, it is noted that each mass slides off at a different frequency of rotation of the table. Table 1 shows the frequency at which each mass slides off.
d on the table before placing the masses. Explain the effect of this on the frequency at which each mass slides off.
Date posted: June 2, 2017. Answers (1)
- Figure 12 shows masses A, B and C placed at different points on a rotating table. The angular velocity, of the table can be varied. (Solved)
Figure 12 shows masses A, B and C placed at different points on a rotating table. The angular velocity, of the table can be varied.
State two factors that determine whether a particular mass slides off the table or not.
Date posted: June 2, 2017. Answers (1)