*Question*

An object falls freely from rest in a vacuum. The graph shows the variation with time *t* of the velocity *v* of the object.

Which graph, **using the same scales**, represents the object falling in air?

**Answer/Explanation**

Ans: **C**

The velocity in free fall is given as,

v = gt

since g is constant, therefore the velocity increases at a constant rate, hence the graph (A) showing a straight line, is the correct answer.

### Question

Which statement must be true for an object in a gravitational field?

**A** If the object has mass then the field causes it to accelerate.

**B** If the object has mass then the field causes it to have weight.

**C** If the object has weight then the field causes it to accelerate.

**D** If the object has weight then the field causes it to have mass.

**Answer/Explanation**

Ans:**B**

An object in a gravitational field experiences a force due to the gravitational field, this force causes it to have weight. Hence the option (B) is correct.

*Question*

The graph shows how quantity P varies with quantity Q for a body falling vertically downwards in a uniform gravitational field with air resistance.

Which pair of quantities could be represented by P and Q?

**Answer/Explanation**

Ans: A

For a body falling under uniform gravitational field, the acceleration decreases with the increase in the air resistance, therefore the first option is correct if P is the acceleration and Q is the air resistance.

(B) If there is no air resistance, then the acceleration remains constant with time therefore this option is incorrect.

(C) The velocity first increases and then becomes constant and does not go to zero therefore the option is incorrect.

(D) Since the velocity does not go to zero with time hence this option is also incorrect.

*Question*

The graph shows how quantity P varies with quantity Q for an object falling in air for a long time in a uniform gravitational field.

**Answer/Explanation**

### Question

A skydiver, who is falling vertically through the air, opens his parachute.

Which row describes the velocity of the skydiver immediately after he opens his parachute?

**Answer/Explanation**

Ans

**A**