Motion Questions

[nisha]

Honestly, these questions are so easy....yet I cant remember how to do them, and my teacher told me to stop pestering her. So here we go:

Q8. Vinh is investigating the bouncing ability of a golf ball and a tomato. He drops both objects from a height of 2.00m and measures the rebound heights. He found that the golf ball rebounded to 1.50m and the tomato just splattered without rebounding at all.
(a) Calculate the speed of the golf ball as it rebounded
(b) which objects experienced the greater change in velocity as it landed? Calculate the velocity change of this object

Q9. Fiona rides her skateboard up a ramp. She begins with a speed of 8.0m/s but slows with a constant deceleraton of 2.0m/s/s. She travels some distance up the ramp before coming to rest, then rolls down again. Ignoring air resistance and friction, calculate:
(a)the distance that Fiona travels up the ramp before stopping
(b) the time that it takes Fiona to reach this highest point
(c) Fiona's velocity after 5.0 seconds have elapsed


For question 9, do I have to draw a v/t graph?

Also, what can I do to perform better in Motion? I understand the main concepts quite well, but Motion is the section that screwed me up in last years exam, and I dont want that to happen in the future.......

[Mr. Study]

For Question 9, Couldn't you use one of the five equations of motion?

You have initial velocity, final velocity and acceleration.

To perform better in motion, this is how I did it. Questions! I did questions that related to real life and hence, made a connection. Try some Khan Academy videos or MIT open lectures, they explain concepts, in my opinion, pretty well. It also gives a different take/view on how to view concepts.

Try starting of with the basic 5 equations of motions, heres a great website: http://www.physicsclassroom.com/class/1dkin/u1l6d.cfm.

After that you can do some extended response questions from your textbook.

Hopefully that helps a bit.

Got beaten. xD

[Phy124]

8.a)
To calculate the initial speed of the golf ball as it leaves the ground:
v² = u² + 2as
0 = u² + 2 x - 9.8 x 1.5
u = (29.4)^1/2 = 5.42 m/s

b)
For both objects - to calculate the speed they hit the ground:
v² = u² + 2as
v² = 0 + 2 x 9.8 x 2
v = (39.2)^1/2 = 6.26 m/s

Change in v for golf ball:
= v_final - v_initial
= -5.42 - 6.26 = -11.68 = 11.68 m/s in opposite direction to initial (I'm not sure about those units  )

Change in v for tomato:
= v_final - v_intial
= 0 - 6.26 = -6.26 = 6.26 m/s in the opposite direction to initial (I'm not sure about those units  )

Therefore, the golf ball has a greater change in velocity

9. a)
v² = u² + 2as
0 = 8 + 2 x -2 x s
-8 = -4s
s = 2m

b)
v = u + at
0 = 8 +-2t
-8 = -2t
t = 4s

c)
Give that 4 seconds have already elapsed (calculated in b) we need to find her velocity after 1 second of falling down the ramp:
v = u + at
v = 0 + 2 x 1
v = 2m/s

In the above equations; a = acceleration, u = initial velocity, v = final velocity, s = distance traveled, s = time taken/elapsed

As of yet, I haven't read over this work to ensure all answers are correct, I'll do that now.