Aisha dropped an object of mass 4 Kg from a height of 10m.
10)
The object has a speed of 0 m/s at position A and is at a height
of 10m above the ground. At position B, the object is 6m above
the ground. At position C, the object is 4m above the ground.
At point D, the object is mere picometer ( almost at 0 meter height)
above the ground. Assume negligible air resistance throughout
the motion. Use this information to fill in the table. (g=10m/s2)
Answers
Explanation:
The object has a speed of 0 m/s at position A and is at a height
A of 10m above the ground.
To find : Velocity & time taken to reach at B , C & D
Solution:
At t = 0 position A - 10 m above ground velocity = 0
PE = mgh = 4 * 10 * 10 = 400 Joule
KE =(1/2)mv² = 0
At position B - 6 m above ground distance covered (10 - 6) = 4 m
S = ut + (1/2)at²
u = 0
a = g = 10
=> 4 = (1/2)(10)t²
=> t = √0.8 = 0.9 sec
V = U + at = 9 m/s
PE = 4 * 10 * 6 ≈ 240 joule
KE = 400 - 240 ≈ 160 Joule
At position C - 4 m above ground distance covered (10 - 4) =6 m
S = ut + (1/2)at²
u = 0
a = g = 10
=> 6 = (1/2)(10)t²
=> t = √1.2 ≈ 1.1 sec
V = U + at ≈ 11 m/s
PE = 4 * 10 * 4 = 160 joule
KE = 400 - 160 = 240 Joule
At position D - 0 m above ground distance covered (10 - 0) =10 m
S = ut + (1/2)at²
u = 0
a = g = 10
=> 10 = (1/2)(10)t²
=> t = √2 = 1.4sec
V = U + at = 14 m/s
PE = 4 * 10 * 0 = 0 joule
KE = 400 Joule
Position Distance from ground PE KE Time Velocity
A 10 m 400 0 0 s 0 m/s
B 6 m 240 160 0.9 s 9 m/s
C 4 m 160 240 1.1 s 11 m/s
D 0 m 0 400 1.4 s