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# m2 quick question watch

1. https://ca99c64778b62ba7e7b339967029...%20Edexcel.pdf

for q6 part b, how do we know which value of t to use from the quadratic?

thanks
2. (Original post by Katiee224)
https://ca99c64778b62ba7e7b339967029...%20Edexcel.pdf

for q6 part b, how do we know which value of t to use from the quadratic?

thanks
For the smaller time the ball would still be travelling upwards so it would hit the platform from underneath and therefore not land on the platform. But for the larger time the ball is then travelling downwards and thus can land on the platform. This can also be seen from the diagram that the velocity must be negative as it is travelling downwards at the point the ball reaches the platform.
Hope this helps.
3. (Original post by Katiee224)
https://ca99c64778b62ba7e7b339967029...%20Edexcel.pdf

for q6 part b, how do we know which value of t to use from the quadratic?

thanks
Because you're resolving vertically, the particle will be at the height 4.9m twice. You want to choose the larger time because that is when the particle is at the same height as B for the second time.
4. oh yeah how silly of me, thanks guys

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