A rock is thrown vertically upward from the edge of a cliff. The rock reaches a

Question

A rock is thrown vertically upward from the edge of a cliff. The rock reaches a maximum height of 10.0 m above the top of the cliff before failing to the base of the cliff, landing 8.00 s after it was thrown. How high is the cliff? Between take off and landing, an airplane accelerates at a constant from 250 km/h to 950km/h over 30 min. Right after 30 min acceleration, the pilot realizes something wrong with the engine, instantly decelerates to stop over 20mins. Find the total distance traveled by the plane. A girl drops a rock from the edge of a cliff and observes that it strikes the bottom 6.00 s later. How high is the cliff? A ball thrown vertically upward has an upward velocity of 8.00 m/s at a point 20.0 m above where it was thrown. How long does the ball take to reach that point? And what maximum height the ball can reach? 5 The brakes are applied to a car travelling on a dry, level highway. A typical value for the magnitude of the car s acceleration is 2.50 m/s^2. If the car's initial speed is 60.0 m/s, how far does it travel, starting from the moment the brakes are applied?

Explanation / Answer

Let height of the cliff = h

Height from the top of the cliff = 10m

time of raise = sqrt(2h/g) = sqrt(2*10/9.8) = 1.43s

time of fall = 8-1.43 = 6.57 s

height of th cliff h = gt2/2 = 9.8*6.572 /2 = 211.5 m

2) initial speed u = 250 km/hr = 69.44 m/s

final speed    v = 950 km/hr = 263.89 m/s

acceleration   = (263.89 - 69.44)/1800 = 0.108 m/s2

initial speed at take over   = 0

final speed = 263.89 m/s

acceleration = 0.108 /s2

distance traveled s = v2 /2a = (263.89)2 /2*0.108 = 644.796 km

deceleration time =20 min.

initial speed = 263.89 m/s

final speed =0

distance traveled = 263.89*1800/2 = 237.5 km

Total distance traveled   = 644.796 + 237.5 = 882.3 km

3: time t = 6s

h = gt2/2 = 9.8*62 /2 = 176.4 m

4. vertical vel (final) v = 8.0 m.s

distance traveled = 20m

intial velocity u = ?

v2 - u2 = - 2gh

u2 = 82 + 2*9.8*20

u = 21.35 m/s

v = u-gt

t = (21.35- 8.0 )/9.8 = 1.36 s

maximum height   = u2/2g = 23.26 m

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