- #1

Hello, i'm new and need help! Here's the deal...

You have a hockey puck that's mass 2.5lbs. You shoot it up a ten degree incline at 8ft/sec. The friction factor on the ramp is .08. You are trying to reach a hole that is 10 feet away. Does the puck make it?

In trying this problem for the last three days, I have had several different answers, but none make much sense.

Do you have to convert the 2.5lbs to mass in order to get the answer? I've tried changing it (2.5lbs) to force (N), but then get stuck after I add up all the forces acting on the puck and make them equal to mass X acceleration.

My prof. said you have to convert lbs. to force which I did, but I still think you need to get the mass.

Any help or suggestions would be greatly appreciated.

Evelynn

Just read the rules...

As for work I don't have the exact numbers right in front of me, but I'll do my best.

First, 2.5lbs = -11.12 N that's the force of gravity (I'm assuming)

Then, cos 10 * 11.12N to get the Normal force

then sin 10 * 11.12N to get the x component of gravity force

then .08 * Normal force to get the friction force (negative)

Then you add the Friction force & the X component of gravity and set that = to mass * acceleration. (Am I right so far?)

Here's where i get stuck. I've tried using the 2.5 as the mass, and I've tried converting the 2.5 (as a weight) to mass by dividing by 32 ft/sec.

Anyway, after you get acceleration you can use the kinmatics equations to get time and final position...which you want to know if it is around 10 ft. The final answers I've gotten are either 13.something, or 1.something. And I've tried manipulating the numbers through conversions of feet to meters, but just get even more confused.

P.S. Do I need to change all my units to m/s?

You have a hockey puck that's mass 2.5lbs. You shoot it up a ten degree incline at 8ft/sec. The friction factor on the ramp is .08. You are trying to reach a hole that is 10 feet away. Does the puck make it?

In trying this problem for the last three days, I have had several different answers, but none make much sense.

Do you have to convert the 2.5lbs to mass in order to get the answer? I've tried changing it (2.5lbs) to force (N), but then get stuck after I add up all the forces acting on the puck and make them equal to mass X acceleration.

My prof. said you have to convert lbs. to force which I did, but I still think you need to get the mass.

Any help or suggestions would be greatly appreciated.

Evelynn

Just read the rules...

As for work I don't have the exact numbers right in front of me, but I'll do my best.

First, 2.5lbs = -11.12 N that's the force of gravity (I'm assuming)

Then, cos 10 * 11.12N to get the Normal force

then sin 10 * 11.12N to get the x component of gravity force

then .08 * Normal force to get the friction force (negative)

Then you add the Friction force & the X component of gravity and set that = to mass * acceleration. (Am I right so far?)

Here's where i get stuck. I've tried using the 2.5 as the mass, and I've tried converting the 2.5 (as a weight) to mass by dividing by 32 ft/sec.

Anyway, after you get acceleration you can use the kinmatics equations to get time and final position...which you want to know if it is around 10 ft. The final answers I've gotten are either 13.something, or 1.something. And I've tried manipulating the numbers through conversions of feet to meters, but just get even more confused.

P.S. Do I need to change all my units to m/s?

Last edited by a moderator: