# PHY101 Assignment Number 1 Idea Solution 2019

Question # 1

a) A ball will land at the same time if you drop it straight down from the top of a building or
if you throw it out horizontally. Either yes or no explain it. Marks = 7
Ans:
No, the straight downward ball will hit the ground first. Because when we throw ball
straight downward the whole work will be done by Y component and X component’s work will
be zero. But it horizontal case, there will be a projectile, at first whole work will be done by X
component and Y component’s work will be zero. Gradually the workload will shift to Y
component. But we need Y component’s work only so that the angle of throw is exactly
opposite to normal.

b) Is it true or wrong to say that, Vectors always start at the origin? Either yes or no justify it.
Marks = 5
Ans:
No, it isn’t necessary to take position vector from origin only. You can choose to
have coordinates (1,2,3) also as the reference point or for that matter any point
on the XYZ plane. But then you must stick to that reference point only while
working on a problem. Ans:
Force along x axis
Fx = Fcos(60)
= 260(0.5)
Fx = 130N
Force along y axis
Fy = Fsin(60) – mg
= 260(0.866) – 1.4
Fy = 223.77N
Mass of ball
we know that:
mg = 1.4N
m = 1.4/9.8
m = 0.143kg

Acceleration along x axis
Fx = ma(x)

a(x) = Fx/m
= 130/0.143
a(x) = 909.1 m/s2
Acceleration along y axis
Fy = ma(y)
a(y) = Fy/m
= 223.77/0.14
a(y) = 1598.357 m/s2 