Kinematics Word Problems

1. Oct 9, 2014

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 travelling 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.

2. Oct 9, 2014

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?

3. Oct 9, 2014

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.

4. Oct 9, 2014

Fist of Justice

For #3, I think it's this

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

Am I right?

5. Oct 9, 2014

Staff: Mentor

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.

6. Oct 9, 2014

Staff: Mentor

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