Transcript Lesson 3 – Acceleration and SUVAT 2

A LEVEL PHYSICS
Year 1
Free fall and SUVAT
A*
A
B
C
•I can describe how the velocity
of an object in free fall changes
as it falls (grade d)
•I can mathematically show that
two objects of different mass fall
at the same rate (grade c)
•I can use SUVAT equations to
calculate the parameters of falling
objects (grade b)
B/C
Target
A/A*
Target
EP
EP
EP
EP
AEP
EP
Galileo Galilei
When dropped from the same height which
object hits the ground first?
Falling Objects
• Any two objects accelerate at the same rate due to the
force of gravity
• Constant Gravitational force = constant acceleration
• Mass has no effect
• Surface area increases drag (air resistance)
Freefalling
• Plot a graph of s against t2:
No. of
flashes
0 2
Time /s
Distance
fallen/ m
3
4
5
6
7
8
9
0 0.06 0.10
0.13
0.16
0.19
0.23
0.26
0.29
0 0.02 0.04
0.07
0.12
0.17
0.24
0.33
0.42
• Considering s=ut + 1/2at2
calculate the acceleration due to
gravity. (Hint: compare it to
y=mx+c)
Proving it mathematically
• Use the equation below to prove that two
objects will hit the earth at the same point:
s = ut + ½ at2
Quick Questions
1.
2.
3.
A pebble released from rest on a bridge hit the water below 0.9s
later. Calculate the distance it fell and its speed upon hitting the
water.
A spanner was dropped from a hot air balloon when the balloon
was at rest 50m above the ground. Calculate the time take and the
velocity.
A bungee jumper jumped off a platform 75m above a lake.
Releasing a small object the instant she left the platform.
a)
b)
4.
Calculate the time taken by the object to fall and the speed (assume air resistance is
negligible).
Describe how long the bungee jumper would take to descend relative to the object.
Explain why.
An astronaut on the moon threw an object 4.0m vertically upwards
and caught it 4.5 seconds later.
a)
b)
Calculate g on the moon and the speed of projection of the object.
How high would the object have risen on earth from the same projection?
Quick Answers
1.
2.
3.
4.
4.0m, 8.8m/s
3.2s, 31m/s
3.9s, 38m/s
1.6m/s, 3.6m/s, 0.64m