# Physics - HELP!

[SOLVED] Physics - HELP!

Hey guys,

Currently taking Grade 12 Advanced Placement Physics. I'm craming for a kinetics test tomorrow, which I will do reasonably well. However, I am still stumped on solving Motion of 2 Dimensions using the "Component Technique". I am able solve it using the Sine and Cosine laws, but I have to be able to solve it using both.

If anyone could help me out by taking a shot at explaining it, it would be very much appreicated.

A sample problem:

A passenger in a hot-air balloon throws a ball with an initial unknown velocity. The ball accelerates at 9.8m/s/s [down] for 2.0s, at which time its instantaneious velocity is 24m/s [45 degrees below the horizontal]. Determine the ball's initial velocity.

Again, any help would be greatly appreciated.

Last edited by a moderator:

Tyro
After 2 seconds,
Vx^2 + Vy^2 = 24^2

With the 45 degree angle thing, conclude Vx = Vy at this time

Vx = (576/2)^0.5
= 16.97ms-1
Vy = 16.97ms-1

Assume horizontal velocity unchanged over 2s. Ux = Vx = 16.97ms-1

Uy = Vy - 9.81*2
= - 2.63ms-1

Note: 'U' refers to initial velocities, 'V' to end ones, 'x' to horizontal direction, 'y' to vertical.

Initial speed = 17.17ms-1