A projectile is thrown up with the initial speed u, making an angle theta (theta > 45 deg) with the horizontal. What is the time, just after which, it will be moving perpendicular to its initial direction of motion?
a) #u/(gsintheta)#
b) #(usintheta)/g#
c) #u/(gcostheta)#
d) #(ucostheta)/g#
a)
b)
c)
d)
1 Answer
THe answer is option
Explanation:
Reminder :
The initial speed is
The angle is
Initial conditions
The components of the speed are
The components of the speed after time
The acceleration due to gravity is
Writing the components of the speed in vector notation
In order for the projectile to move perpendicular to the initial direction, the dot products