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# M1 question, position vectors Watch

1. So I have two questions,

The first one is a model helicopter has initial position 80J M and flies with a constant velocity with (6i - 3j) Ms, A model aeorplane flies at the same heigh as the helicopter. Its initial position is 10j m and its initial velocity is 5i Ms and its acceleration is (0.1i + 0.05j) ms. Find the experession for the position vectors, and the copter and the plane collide find the time when this occurs and the position of the collission,

The first part finding the expression is simple, the bit about the time? which component do I put = to 0 to find T. The J component of the helicopter or the aeroplane? When I do put the component of the aeroplane = to 0 I get T as 20, but how do I show this for the helicopter as when I put that = 0 I dont get 20.
2. (Original post by SunDun111)
So I have two questions,

The first one is a model helicopter has initial position 80J M and flies with a constant velocity with (6i - 3j) Ms, A model aeorplane flies at the same heigh as the helicopter. Its initial position is 10j m and its initial velocity is 5i Ms and its acceleration is (0.1i + 0.05j) ms. Find the experession for the position vectors, and the copter and the plane collide find the time when this occurs and the position of the collission,

The first part finding the expression is simple, the bit about the time? which component do I put = to 0 to find T. The J component of the helicopter or the aeroplane? When I do put the component of the aeroplane = to 0 I get T as 20, but how do I show this for the helicopter as when I put that = 0 I dont get 20.
You don't put anything equal to zero.

When two things collide they must be in the same position.

So you set their positions equal to each other and solve for t.
When they collide their i components will be equal and the their j components will be equal. Two simultanseous equations to solve.

Post some working if you're still stuck.
3. (Original post by ghostwalker)
You don't put anything equal to zero.

When two things collide they must be in the same position.

So you set their positions equal to each other and solve for t.
When they collide their i components will be equal and the their j components will be equal. Two simultanseous equations to solve.

Post some working if you're still stuck.
Simultaneus equation doesnt give me the answer? The answer is actually 20 seconds, and when I solve for the J notation for the plane = 0 and solve for T I get the answer, Dosent this work since they are at the same position If i put each of the J notation = to 0 I should get the answer?
4. (Original post by ghostwalker)
You don't put anything equal to zero.

When two things collide they must be in the same position.

So you set their positions equal to each other and solve for t.
When they collide their i components will be equal and the their j components will be equal. Two simultanseous equations to solve.

Post some working if you're still stuck.
Dm I figured it out thanks i get you

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