M1 past exam Q

Hi everyone i'm just doign a past exam paper and have found a question I can't do. It is similar to the one posted below. a tile of mass 2kg slides 1.2m from rest down a roof inclined at 30 degrees to the horizontal against a resistance of 5N. The edge of the roo is 3m above the ground.
I have already worked ou the acceleration, the velocity of the tile at the edge of the roof. But now it ask how long it takes to hit the ground and the horizontal distance from the end of the roof where it lands.

I don't understand how to work this out can anyone help me.

Reply 1

sonic7899

yehthis is the kind of thing i am doing on forces at the minute but I have not done a question like that sorry.

Reply 2

Hearing Voices

Once it is off the roof downwards acceleration will simply be g.

The horizontal velocity will stay constant at the same value of the horizontal component of the velocity when it leaves the roof.

To work out how long it takes to hit the ground you should just act as though the item has been dropped (with an initial velocity from the vertical component of the velocity when it leaves the roof) and see how long it takes to hit the floor.

For the horizontal distance, I'd use distance = speed x time :smile:

I hope this helps :smile:

Reply 3

Big_Sam

I have just tried doing your method but the answer doesn't seem to come out right

Reply 4

Gymnosopher

Does it travel 1.2 meters to the edge of the roof? If the particle (tile) comes off at this point you'll need to resolve the velocity horizontally and verticaly - so it's travelling 30 degrees from horizontal at your velocity, seperate this with Vsin30 and Vcos30.

Now you've got 2 equations to do. First, the tile will be acting under gravity vertically, and s=ut + 1/2at^2 (distance 3m = initial velocity downwards [after resolving it]multiplied by time, plus half acceleration multiplied by time squared). Putting in your variables you can rearrange to find time.

When you have time, the horizontal distance from the room is just your basic s=vt, as there is no acceleration further this way - it travels constantly untill hitting the ground (which is the time it reaches it from the verticle distance).

Hope this helps / is right, I've not done M1 in a while :smile:

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