Kinematics: Solving Questions on Speed, Distance, Time & Acceleration

[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?

 

[206PiruBlood]

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

I suggest you make an attempt

 

[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 can't seem to get the ones i need right.

 

[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

 

[the pro]

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

a) 0.13424051
b)588.495976
s)79.0

 

[mvantuyl]

a) 0.13424051
b)588.495976
s)79.0

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?

 

[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