Projectile motion

Question 1

What happens to a ball dropped and a ball thrown?

Answer 1

• A ball thrown horizontally from the top of a tower will fall to at the same rate as a ball dropped from the top of the tower.
• Both ball accelerate towards the ground.

Question 2

What is the trajectory of a ball thrown horizontally?

Answer 2

Parabolic

Question 3

What is the horizontal force on a ball?

Answer 3

There is no horizontal force on the ball (if you neglect air resistance).

Question 4

What is the horizontal velocity on a ball?

Answer 4

The ball has a constant horizontal velocity.

Question 5

What did Newton suggest would happen if you kicked a ball hard enough?

Answer 5

Newton suggested that if the ball could be kicked hard enough from a very tall peak, it would never hit the ground but stay in orbit. Gravity would make the ball fall to the Earth but never reach it because of the Earth’s curvature this is a principal use to put satellite into orbit.

Question 6

The four equations of motion can be applied to projection:

Answer 6

• v = u + at
• s = ½ (u + v)t
• s = ut + ½at²
• v² = u² + 2as

Question 7

The photograph taken with a stroboscopic light shows:

Answer 7

• The horizontal speed is constant.
• The ball slows down as it goes up.
• The ball speeds up as it falls down.

Question 8

What is the only force on a ball?

Answer 8

A vertical force due to gravity. There is a downward acceleration of 10 m/s².

Question 9

Force Eq.

Answer 9

force = mass x acceleration

Question 10

What is velocity?

Answer 10

Velocity is a vector - it has magnitude and direction.

Question 11

What is the resultant velocity?

Answer 11

The resultant velocity is the vector sum of the constant horizontal velocity, v_h and the vertical velocity, v_v.