Homework Help: Kinematics questions

1. Oct 10, 2009

jimlee4262

1.A stone is thrown vertically upward with a speed of 11.0 m/s from the edge of a cliff 79.0 m high (Fig. 2-32).

(a) How much later does it reach the bottom of the cliff?

(b) What is its speed just before hitting?

(c) What total distance did it travel?

2.If a car rolls gently (v0 = 0) off a vertical cliff, how long does it take it to reach 74 km/h?

3.A sports car accelerates from rest to 99 km/h in 6.2 s. What is its average acceleration in m/s2?

2. Oct 10, 2009

206PiruBlood

Most of these can be solved once you set up an equation of motion representing your situation.

I suggest you make an attempt

3. Oct 10, 2009

jimlee4262

yes i figured out the last two but the first one i am having trouble on... I found most of the missing variable but i cant seem to get the ones i need right.

4. Oct 11, 2009

jimlee4262

the answers i have gotten for the first one is
A) 5.12
B)-39.3
C)-91.3
Can someone tell me if i did this wrong and help me

5. Oct 11, 2009

the pro

a) 0.13424051
b)588.495976
s)79.0

6. Oct 11, 2009

mvantuyl

a) 0.13424051s doesn't leave much time to reach the maximum height and then fall 79m plus the additional height achieved by the 11.0m/s initial velocity.
b) Accelerating to 588.495976m/s in 0.13424051s would require that acceleration due to the force of gravity is 4380.1979 m/s2
c) What about the distance upward due to the initial velocity of 11.0m/s?

7. Oct 11, 2009

mvantuyl

I came up with
a) 5.29 s
b) 40.9 m/s (the problem asks for speed, which is the absolute value of velocity)
c) 91.4 m