If you throw a ball upward with an initial velocity of 30 m/s, what is its velocity after 4 seconds? 5. If?

If you throw a ball upward with an initial velocity of 30 m/s, what is its velocity after 4 seconds?











5.


If you throw a ball straight up its acceleration at the top of its motion:





A depends on its initial velocity.


B depends on the mass of the ball.


C is 9.8 m/s2


D depends on how high you throw it.


E is 0 m/s2











6. Chris is upset about the recent decision to make Pluto a “dwarf planet”. He figures if Pluto’s acceleration due to gravity is as big as the other planets it should be a “normal” planet. To measure the acceleration on Pluto he dropped a bowling ball 1 meter to the surface. If the time he measured was 1 second what is the acceleration on Pluto








7. Which of the following statements is not suggested when solving kinematic problems?





a Write down the given quantities as well as what you want to know.


b Memorize the equations.


c Keep track of units.


d Draw a picture.


e Consider if the answer is reasonable.





You throw a ball straight up and catch it 2 seconds later at the same position it was thrown. How fast was the ball moving when it left your hand? (Assume the acceleration due to gravity is 10 m/s2)If you throw a ball upward with an initial velocity of 30 m/s, what is its velocity after 4 seconds? 5. If?
So you slept through class? I will set these up for you but wont solve them completely...





1. Okay use what we know; Vo=30m/s, a= -9.81m/s^2 (Speed of gravity and sense they threw it up with a positive and gravity goes down we will assume they want gravity as a negative) t=4s





V=Vo+at





This one is straight forward, there is no algebra or anything... Just plug in your numbers and solve for V.





2. Acceleration is a constant (at least in this set) so as long as you know what are constant acceleration is then you got it. (Hint we used it in the last problem)





3. Okay again what do we know Vo=0, Xo=0m, X=1m , t = 1s





Your formula is X= Xo + Vot + 1/2at^2 It looks like a monster but it's really not. Solving algebraically for a and getting rid of Xo and Vot (because their both zero) leaves us with...





a= 2x/t^2





Just plug in your numbers and solve.





4. The exact answer they want is in your book but I imagine it is B





5. Okay what do we know? t= 2s, a=-10m/s^2





Okay we will use this formula X=Xo+Vot+1/2*at^2


We need to solve for Vo .... now X - Xo is DeltaX and since we started and stopped in the same spot DeltaX=0 therefore...





-Vot + X - Xo = at^2/2 we can simply remove DeltaX now and move the t from Vot and flip the signs and you have solved for Vo





Vo= - at^2/2t Now just plug in your numbers and goIf you throw a ball upward with an initial velocity of 30 m/s, what is its velocity after 4 seconds? 5. If?
use the equation v=u+at, as the ball is thrown upwards the a (being acceleration is negative and equal to -g i.e -9.8m/s^2) if u = 30m/s (initial) then:





v = u + at


v= 30 + (-9.8 x 4)


v = -9.2 m/s