What is the initial velocity of the ball on a smooth ramp?

[Fist of Justice]

Hi, I am new to Physics. I'm having trouble solving these word problems. For the third question I need to find the time first and then the initial velocity?

1. A young girl gives her toboggan a push of 4.0 m/s up a hill. It slides up the hill slowing down at an acceleration of 8.0 m/s2 [down]. It comes to a stop and then slides back towards her speeding up at the same rate as it slowed down on the way up. If the girl has to run 48 m down the hill from where it first was pushed to get to where her sled stopped, find the elapsed time for the journey.

2. A porpoise jumps straight up and crashes back into the water at 8.9 m/s. The drag and buoyancy forces of the water slow the porpoise down with an acceleration of -9.3 m/s2 as the porpoise finally slows to a stop. Find the depth the porpoise reaches.

3. Sanna rolls a ball up to another person on a smooth ramp 19.6 m above her. The ball reaches the other person’s hands when it is traveling 4.9 m/s uphill. If the ramp angle slows the ball down by 3.7 m/s each second it travels up the ramp, find the initial velocity of the ball.

 

[Greg Bernhardt]

What parts are you having trouble with? Start with telling us what you know or how far you've gotten. Are these homework?

 

[Fist of Justice]

No this is exercise for my exam, but I don't have the solutions to these questions. I've been trying to figure out these questions forever.

 

[Fist of Justice]

For #3, I think it's this

½mvo² = ½mv1²+mgh
vo = √(v1²+2gh) = 20 m/s

Am I right?

 

[Nugatory]

You have three problems here. Start a separate thread for each one in the introductory physics homework section (and please do use the template that appears when you start a thread there) and you'll get much better and more heful answers.

 

[Nugatory]

Locking this thread, but only so that the discussion can be restarted in the homework forums.