Equations of uniformly accelerated motion
4 marks · NormalA small parcel falls from rest from a hot air balloon. The balloon is at a height of 180 m above the ground. Assume the acceleration due to gravity is 10 m/s² and air resistance is negligible.
Calculate the speed of the parcel just before it hits the ground.
State the value of the initial velocity of the parcel.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) 60 m/s · must show Use v^2 = u^2 + 2as with u = 0, a = 10, s = 180, Correct substitution, Square root to get final answer
(b) 0 m/s · must show States initial velocity as zero
Common mistakes: Using wrong sign for acceleration; Using wrong value for initial velocity
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Substitutes values correctly into v^2 = u^2 + 2as.
M2 (a) · 1 mark · Correctly rearranges to find v and attempts square root. (follow-through)
A1 (a) · 1 mark · Arrives at v = 60 m/s (accept 60.0 or values within 0.5). (follow-through)
B1 (b) · 1 mark · States initial velocity is 0 m/s.
Worked solution
a) Use the equation:
Here, u = 0 m/s, a = 10 m/s², s = 180 m.
The speed is 60 m/s.
b) The parcel starts from rest, so the initial velocity is 0 m/s.