# 3i Infotech Papers: Sample Questions 857 - 858 of 1245

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## Question number: 857

MCQ▾

### Question

When a bicycle is in motion, the force of friction exerted by the ground on the two wheels is such that it acts

### Choices

Choice (4) Response

a.

In the backward direction on both the front and rear wheels.

b.

In the forward direction on the front wheel and in the backward direction on the rear wheel.

c.

In the backward direction on the front wheel and in the forward direction on the rear wheel.

d.

Question does not provide sufficient data or is vague

a.

### Explanation

• Pedalling the bicycle merely rotates the back wheel in clockwise sense.

• The velocity of point of contact is therefore backwards, so, friction must act forward on the rear wheel.

• This frictional force causes a translational acceleration of the entire bicycle, including the front wheel.

• The velocity of point of contact tends to develop in the forward direction so friction acts in the backward direction.

Similar reasoning applies to a car, for the engine merely rotates the back wheel.

## Question number: 858

MCQ▾

### Question

Without the use of Cartesian product, how many joining conditions are required to join tables?

### Choices

Choice (4) Response

a.

2

b.

4

c.

1

d.

3

d.

### Explanation

• To join ‘n’ tables ‘n-1’ conditions should be satisfied so to join tables conditions should be satisfied.

• Join is used to collate data from two more tables- joined to appear as single table of data.

• Combines columns from two or more tables by using values common to both table.

• “Join” keyword is used in SQL queries for joining two or more tables.

• Minimum required condition for joining table is (n-1) where n, is number of tables.

• A table can also join to itself, which is known as self join.