# Homework Help: Force on projected object at its highest point. What is the net force?

1. Sep 20, 2009

### peterpam89

1. The problem statement, all variables and given/known data
A ball with a weight of 1.0 N is thrown at an angle of 30 degrees above the horizontal with an initial speed of 12 m/s. There is no air resistance acting on the ball. At its highest point, the net force on the ball is:
A. 4.9 N, 30 degrees below horizontal
B. zero
C. 4.9 N up
D. 4.9 N down
E. None of the above

2. Relevant equations
Fnet= ma

3. The attempt at a solution

I am guessing that since there is no wind resistance, there is no acceleration in the X direction. Thus, the horizontal force is zero.

The force in the y direction should remain constant because gravity is a constant (9.8 m/s^2) and the mass is a constant. Thus, I am thinking that the net force should equal 1N.

Thank you so much!
-peterpam89

2. Sep 20, 2009

### pgardn

I would say your reasoning is spot on.

I hope I did not break any forum rules,
if so, I apologize.

3. Sep 20, 2009

### ideasrule

Yup, it's 1 N. Gravity is the only force that can possibly act on the mass: there's no air resistance, friction, electromagnetism, nuclear forces, or divine intervention to consider, so the net force is due only to gravity and gravity exerts 1 N.

4. Sep 20, 2009

### peterpam89

Great- thanks!