Year 12s: what will be the first way you research your future options? >>

Motion and Force equation

Hi guys, I was wondering if you could help me understand this question:

A bullet is fired horizontally at a speed of 200ms-1 at a target which is 100m away. How far has the bullet fallen when it hits the target?

I think I understand that you need to treat the vertical and horizontal velocities as two different bodies of equations but other than that I'm stuck.

Reply 1

Doglamlico

Original post by Coracaldo

I think I understand that you need to treat the vertical and horizontal velocities as two different bodies of equations

You're right about splitting it up into horizontal and vertical velocities.

The first thing to do is find out how long the bullet is travelling for:

Horizontally, you have the initial speed (200 ms^-1), displacement (100m), and acceleration (assume that there is no resistance, i.e. acceleration is 0 ms^-2).

Can you think of which SUVAT you'll need to find the time of flight from these three pieces of information?

Next, you can use this information to find out how far the bullet has fallen:

You have the time of flight (t), the vertical acceleration (~9.8 ms^-2) and the initial vertical velocity (0 ms^-1). Once again you'll need to choose the appropriate SUVAT to find the vertical displacement, i.e. how far the bullet has fallen.

(edited 10 years ago)

Reply 2

Coracaldo

Thanks, I'll see if I can sort something out.

Reply 3

Coracaldo

Original post by The Polymath

You have the time of flight (t), the vertical acceleration (~9.8 ms^-2) and the initial vertical velocity (0 ms^-1).

Sorry but why is the initial velocity 0ms^-1 this time around?

Reply 4

Doglamlico

Original post by Coracaldo

Sorry but why is the initial velocity 0ms^-1 this time around?

Since the bullet was fired horizontally, the vertical component of the velocity is zero. Similarly, if the bullet had been dropped off a cliff, its horizontal velocity would have been zero.

Reply 5

Coracaldo

Original post by The Polymath

Since the bullet was fired horizontally, the vertical component of the velocity is zero. Similarly, if the bullet had been dropped off a cliff, its horizontal velocity would have been zero.