Motion and Time — Science STD 7 — Question

Note the distance between the two stations and the time taken by the different trains to cover such distance. Calculate speeds of the trains and find the fastest and slowest train.

A small amount of hydrochloric acid is always produced in the stomach. Is it useful or harmful for us? If excess of acid is produced in the stomach, what should we do?

You are given six cells marked A, B, C, D, E, and F. Some of these are working and some are not. Design an activity to identify which of them are working.
(i) List the items that you require.
(ii) Write the procedure that you will follow.
(iii) With the items, carry out the activity to identify the cells that are working.

Write short notes on Short Circuiting.

Nitrogen is an essential nutrient for plant growth. But farmers who cultivate pulse crops like green gram, bengal gram, black gram, etc. do not apply nitrogenous fertilizers during cultivation. Why?

Two different type of lenses are placed on a sheet of newspaper. How will you identify them without touching?

Collect some flower of different plants like papaya, rose, mustard, lady’s finger, Petunia, cucumber, corn, pea, etc. Group them under following heads.

1. Which of these plants have unisexual flowers?
2. Which of these plants have bisexual flower?
3. What is the other name of unisexual and bisexual flower?

While learning to ride a bicycle Boojho lost his balance and fell. He got bruises on his knees and it started bleeding. However, the bleeding stopped after some time.

1. Why did the bleeding stop?
2. What would be the colour of the wounded area and why?
3. Which type of blood cells are responsible for clotting of blood?

Explain how the exchange of gases occurs in human beings.

Roots of the plants get oxygen from the air present in the spaces between the soil particles. Find out how the plants living in the marshy areas respire?