Class-8 Science Chapter-11 Force and Pressure

 

Class 8th Science Solutions 

Chapter 11 Force and Pressure

 

Question 1. Give two examples each of situations in which you push or pull to change the state of motion of objects.
Answer:Examples of Pull:

• Pulling of a suitcase
• Pulling of a cow by a man.

Examples of Push:

• Pushing of a car to move
• Pushing of an almirah by a man.

Question 2.Give two examples of situations in which applied force causes a change in the shape of an object.
Answer:Examples of change in shape of an object when force is applied on it:

1. Pressing a ball of dough when rolled to make a chapati.
2. Pressing an inflated balloon between two palms.

Question 3.Fill in the blanks in the following statements:
(a) To draw water from a well we have to at the rope. - pull
(b) A charged body an uncharged body towards it. - attracts
(c) To move a loaded trolley we have to it. - pull/push
(d) The north pole of a magnet the north pole of another magnet. - repels.

Question 4.An archer stretches her bow while taking aim at the target. She then releases the arrow, which begins to move towards the target. Based on this information fill up the gaps in the following statements using the following terms:

(a) To stretch the bow, the archer applies a force that causes a change in its shape.
(b) The force applied by the archer to stretch the bow is an example of muscular force.
(c) The type of force responsible for a change in the state of motion of the arrow is an example of a contact force.
(d) While the arrow moves towards its target, the forces acting on it are due to gravity,.and that due to friction of air.

Question 5.In the following situations identify the agent exerting the force and the object on which it acts. State the effect of the force in each case.

(a) Squeezing a piece of lemon between the fingers to extract its juice.
(a) In this situation, the fingers are the agents exerting a force. Lemon is the object on which force acts. It involves muscular force.

(b) Taking out paste from a toothpaste tube.
(b) In this situation, the fingers are the agents exerting a force. Toothpaste is the object on which force acts. It involves muscular force.

(c) A load suspended from a spring while its other end is on a hood fixed to a wall.
(c) In this situation, the load is the agent exerting force. Spring is the object on which force acts. It involves gravitational force.

(d) An athlete making a high jump to clear the bar at a certain height.
(d) In this situation, the athlete is the agent exercising force, bar is the object to be cleared. It involves a non-contact gravitational force.

Question 6.A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammering affect the piece of iron?
Answer: The force due to. hammering causes the changes in the shape of the iron and iron can be moulded in the shape of the required tool.

Question 7.An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for the attraction between the balloon and the wall?
Answer: This is an electrostatic force.

Question 8.Name the forces acting on a plastic bucket containing water held above ground level in your hand. Discuss why the forces acting on the bucket do not bring a change in its state of motion.
Answer:Forces acting on the plastic bucket are the muscular force and gravitational force. These forces do not bring the change in its state of motion because they are acting in opposite direction with equal magnitude. The effect of the gravitational force will pull it down if the muscular force will grow weak. The body will feel the stretch of gravitational force and will have to bend to cancel the magnitude of gravitational force.

Question 9.A rocket has been fired upwards to launch a satellite in its orbit. Name the two forces acting on the rocket immediately after leaving the launching pad.
Answer:Gravitational force and frictional force.

Question 10.When we press the bulb of a dropper with its nozzle kept in water, air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water gets filled in the dropper. The rise of water in the dropper is due to:
(a) Pressure of water
(b) Gravity of the earth
(c) Shape of rubber bulb
(d) Atmospheric pressure.
Answer:(d) Atmospheric pressure.

Class-7 Sub :Science Chapter 7 Wheater climate and adaptations of animals to climate

 

class-7

science Chapter 7

Weather, Climate and Adaptations of Animals to Climate

 

Question 1:Name the elements that determine the weather of a place.

Answer:The elements that determine the weather of a place are temperature, humidity, rainfall, and wind speed.

Question 2:When are the maximum and minimum temperatures likely to occur during the day?

Answer:The maximum temperature of the day occurs in the afternoon while the minimum temperature occurs early in the morning.

Question 3:Fill in the blanks:

 (i) The average weather taken over a long time is called __climate__.

(ii) A place receives very little rainfall and the temperature is high throughout the year, the climate of that place will be __hot__ and __dry__.

(iii) The two regions of the earth with extreme climatic conditions are _the polar region__ and _the tropical region__.

Question 4:Indicate the type of climate of the following areas:

 (a) Jammu and Kashmir: __Moderately hot and wet__

(b) Kerala: __Hot and wet__

(c) Rajasthan: __Hot and dry__

(d) North-east India: __Wet__

Question 5:Which of the two changes frequently, weather or climate?

Answer:Weather changes frequently.

Question 6:Following are some of the characteristics of animals:

Answer:(i) Diets heavy on fruits → Tropical rainforests

(ii) White fur → Polar regions

(iii) Need to migrate → Polar regions

(iv) Loud voice → Tropical rainforests

(v) Sticky pads on feet → Tropical rainforests

Question 7:The tropical rainforest has a large population of animals. Explain why it is so.

Answer:The climate of tropical rainforests is generally hot and humid with continuous rain. These hospitable climatic conditions support huge populations of plants and animals.

Question 8:How do elephant living in the tropical rainforest adapt itself.

Answer:An important and widely found animal of Indian tropical rainforests is the elephant. It has adapted remarkably to the conditions of this region. Some of the adaptations are as follows.

(i) It uses its trunk as nose so that it has a strong sense of smell.

(ii) Its trunk is also used for picking up food.

(iii) Its tusks are used to tear bark of trees. It can eat barks of trees.

(iv) The soles of their feet are covered with thick pads. These pads can handle their enormous weight. They also prevent sound so that the elephants can move silently.

(v) Its large ears have strong sense of hearing.

Question 9:Choose the correct option which answers the following question:

A carnivore with stripes on its body moves very fast while catching its prey. It is likely to be found in

(i) polar regions

 (ii) tropical rainforests

Answer: (iv) tropical rainforests

Question 10: Which features adapt polar bears to live in extremely cold climate?

(i) A white fur, fat below skin, keen sense of smell.

(ii) Thin skin, large eyes, a white fur.

Answer: (i)A white fur, fat below skin, keen sense of smell

Class-6 Sub Science Chapter-9 The Living And their Surroundings

 

Chapter 9 

The Living Organisms and Their Surroundings

 

Question 1:What is a habitat?

Answer:A habitat is a natural environment where an organism lives. It is basically the address of an organism. Different plants and animals live in different habitats. For example, the habitat of a frog species is fresh water, while the habitat of a camel is a desert.

 Question 2:How is a cactus adapted to survive in a desert?

Answer:A cactus is able to survive in the desert as it is adapted to the hot and humid conditions of the desert. To survive in a desert, the cactus has the following adaptations:

(i) It has long roots that go deep inside the soil for absorbing water.

(ii) Its leaves are present in the form of spines to prevent water loss through transpiration.

(iii) Its stem is covered with a thick waxy layer to retain water.

 Question 3:Fill in the blanks:

 (a) The presence of specific features, which enable a plant or an animal to live in a particular habitat, is called __adaptation__.

(b) The habitats of plants and animals that live on land are called __terrestrial_ habitat.

(c) The habitats of plants and animals that live in water are called __aquatic__ habitat.

(d) Soil, water, and air are __abiotic__ factors of a habitat.

(e) Changes in our surrounding that makes us respond to them are called __stimuli__.

 

Question 4:Which of the things in the following list are non-living?

Plough, Mushroom, Sewing Machine, Radio, Boat, Water Hyacinth, Earthworm

Answer: In the given list, the non-living things are plough, sewing machine, radio, and boat. On the other hand, mushroom, water hyacinth, and earthworms are living things.

 Question 5: Give an example of a non-living thing that shows any two characteristics of living things.

Answer:Car is an example of a non-living thing that shows two characteristics of living things. A car can move from one place to another. Also, it requires energy just like living things.

 Question 6:List the common characteristics of living things.

Answer:6 Some common characteristics of living things are that they

(a) require food

(b) respire and excrete waste material

(c) respond to stimuli in their environment

(d) reproduce to maintain their number

(e) move from one place to another