3.4.1.4 - Projectile Motion

Question 1

How can horizontal velocity be calculated?

Answer 1

Speed = distance / time

Question 2

Say something is thrown at 25ms-1 at 45 degrees how do you work out the vertical component?

Answer 2

25sin45

Question 3

Say something is thrown at 25ms-1 at 45 degrees how do you work out the horizontal component?

Answer 3

25cos45

Question 4

When working out the flight of the projectile what do you use for U and V?

Answer 4

U = vertical component
V = -vertical component

Question 5

What are the two types of friction?

Answer 5

Dry friction and fluid friction.

Question 6

What does resistance depend on?

Answer 6

An increase in speed and the shape of the object.

Question 7

What are projectiles slowed down by?

Answer 7

Air resistance.

Question 8

What is lift?

Answer 8

An upwards force on an object moving through a fluid.

Question 9

Where does lift act?

Answer 9

Perpendicular to the direction the fluid flows in.

Question 10

How does a plan stay flying?

Answer 10

As the wing moves through the air, it pushes down on the air and changes its direction. This causes an equal and opposite reaction force on the wing.

Question 11

In what situation will terminal velocity be reached?

Answer 11

A driving force that stays the same and a frictional or drag force that increases with speed.

Question 12

What are the three main stages of terminal speed?

Answer 12

1. The car accelerates from rest using a constant driving force.
2. A the car speed increases so does the frictional force. This reduces the resultant force on the car, hence its acceleration decreases.
3. Eventually the car reaches a speed where the frictional and driving forces are equal and acceleration = 0.
4. Car continues at a constant speed.

Question 13

Describe the travel of a skydiver.

Answer 13

1. A skydiver will accelerate until the air resistance equals his weight.
2. He will then be travelling at a terminal speed.
3. When his parachute is opened this will increase air resistance. Air resistance is now bigger than his weight.
4. This will slow him down until his speed has dropped enough for the air resistance to again equal his weight. A new terminal speed.