9. Projectile Problem Solving
• Problems in which an object was dropped
with a force in the x- axis
V0
From Free Fall
dy = ½ gt2 dy
dx
10. Projectile Problem Solving
• Problems in which an object was dropped
with a force in the x- axis
V0
From Free Fall
dy = ½ gt2 dy
dx
From Linear Motion
d = v t and that v = d / t
11. Ex. 1 An object travelling at 50 m/s falls out of a
plane. It hits the ground 10 s later. What is the
horizontal distance travelled by the object?
12. Ex. 1 An object travelling at 50 m/s falls out of a
plane. It hits the ground 10 s later. What is the
horizontal distance travelled by the object?
v0 = 50 m/s t = 10 s dx= ?
Solving for the x-axis vector component
• dx= v0t
13. Ex. 1 An object travelling at 50 m/s falls out of a
plane. It hits the ground 10 s later. What is the
horizontal distance travelled by the object?
Solving for the x-axis vector component
• dx= v0t
• dx= (50 m/s)(10s)
• dx= 500 m
** Ch. 3 problem 41 in HW
14. Ex. 2 You want to launch an object from the balcony
into a pool. You are 50 m high and the pool is 10 m
from the bottom of the building. How fast must the
object initially launch in order to reach the pool?
15. Ex. 2 You want to launch an object from the balcony
into a pool. You are 50 m high and the pool is 10 m
from the bottom of the building. How fast must the
object initially launch in order to reach the pool?
• dy = 50 m
• dx= 10 m
• v0 is unknown
v0= dx / t
But wait, t is unknown…..
16. Ex. 2 You want to launch an object from the balcony
into a pool. You are 50 m high and the pool is 10 m
from the bottom of the building. How fast must the
object initially launch in order to reach the pool?
• dy = 50 m
• dx= 10 m
• v0 is unknown
v0= dx / t
But wait, t is unknown….. And we can solve for it
using dy = ½ gt2
17. Ex. 2 You want to launch an object from the balcony
into a pool. You are 50 m high and the pool is 10 m
from the bottom of the building. How fast must the
object initially launch in order to reach the pool?
• dy = 50 m
• dx= 10 m
• v0 is unknown
v0= dx / t
dy = ½ gt2 OKAY – Solve for time
18. Ex. 2 You want to launch an object from the balcony
into a pool. You are 50 m high and the pool is 10 m
from the bottom of the building. How fast must the
object initially launch in order to reach the pool?
• dy = 50 m
• dx= 10 m
• v0 is unknown
v0= dx / t
dy = ½ gt2 OKAY – Solve for time
50 m = ½ (10 m/s2) (t2)
10 s2 = t2 take the square root of both sides
19. Ex. 2 You want to launch an object from the balcony
into a pool. You are 50 m high and the pool is 10 m
from the bottom of the building. How fast must the
object initially launch in order to reach the pool?
• dy = 50 m
• dx= 10 m
• v0 is unknown
v0= dx / t
Knowing that t = 3.16 s, we can now
solve for V0.
v0= dx / t = 10 mproblems 42 s =44 in the hw
**
/ 3.16 and 3.16 m/s
20. Ex.3 You aim an arrow directly at a target
that is 0.2 seconds away. How far below
the target does the arrow hit?
21. Ex.3 You aim an arrow directly at a target
that is 0.2 seconds away. How far below
the target does the arrow hit?
• The only known given is time and we are
determining the distance in the vertical
direction dy.
• Which equation should we use????
22. Ex.3 You aim an arrow directly at a target
that is 0.2 seconds away. How far below
the target does the arrow hit?
• The only known given is time and we are
determining the distance in the vertical
direction dy.
• Which equation should we use????
• dy = ½ gt2
23. Ex.3 You aim an arrow directly at a target
that is 0.2 seconds away. How far below
the target does the arrow hit?
• The only known given is time and we are
determining the distance in the vertical
direction dy.
• Which equation should we use????
• dy = ½ gt2
• dy = ½ (10 m/s2) (0.2 s)2
• dy = 0.2 m ** problem 43
