7.7- PROJECTILE MOTION 1

Question 1

What is a projectile?

Answer 1

object acted upon only by force of gravity

Question 2

What are the 3 key principles to apply to all projectiles?

Answer 2

acceleration of object equal to g + always downwards as force of gravity acts downwards, so acceleration only affects vertical motion of object

horizontal velocity of object constant as acceleration of object doesn’t have a horizontal component

motions in horizontal + vertical directions independent of each other

Question 3

What direction does a projectile move and why?

Answer 3

vertically as it has no horizontal motion

Question 4

For vertical projection what are the equations? (2)

Answer 4

v = u - gt

y = ut - 1/2gt^2

y = displacement

Question 5

When a stone is thrown from a cliff top, what path does it follow?

Answer 5

follows a curved path downwards before it hits the water

Question 6

How can you tell if when a stone is thrown from a cliff top the initial projection is horizontal? (3)

Answer 6

its path through air becomes steeper + steeper as it drops

faster it’s projected, further away it will fall into the sea

time taken for it to fall into sea does not depend on how fast it’s projected

Question 7

When two balls are released at the same time above a level floor such that one ball drops vertically + other projected horizontally, which one hits the floor first?

Answer 7

both hit the floor simultaneously

Question 8

Why do the balls hit the ground at the same time when dropped vertically and projected horizontally?

Answer 8

both pulled to ground by force of gravity, which give both downward acceleration g

ball projected horizontally experiences same downward acceleration as other ball

downward acceleration doesn’t affect horizontal motion of ball projected horizontally- only vertical motion affected

Question 9

What may be used to record the motion of a projectile?

Answer 9

stroboscope and a camera with a slow shutter

Question 10

When the horizontal position of B changes by equal distances between successful flashes, what does this show?

Answer 10

horizontal components of B’s velocity constant

Question 11

The vertical position of A and B change at the same rate. At any instant, A is at the same level as B. What does this show?

Answer 11

A and B have the same vertical component of velocity at any instant

Question 12

When an object is projected horizontally falls in an arc towards the ground, what is the horizontal component of its displacement?

Answer 12

x = Ut

U- velocity
t- time

Question 13

When an object is projected horizontally falls in an arc towards the ground, what is the vertical component of its displacement?

Answer 13

y = 1/2gt