# Physics

posted by on .

I'm having troubles with a few questions.

A tennis ball is thrown vertically upwards. At the top of it's flight, it has:

A. a zero speed and acceleration
B. a zero speed and constant acceleration
C. maximum speed and acceleration
D. maximum speed but zero acceleration
E. none of the above

I think the answer is A, but not quite sure.

Two identical balls are released. One falls in a vacuum and the other through the air. Both balls have:

A. same gravitational force and the same acceleration
B. the same gravitational force acting and different accelerations
C. different gravitational force acting and the same acceleration
D. different gravitational forces acting and different accelerations.

I think D, but I'm not quite sure if there are any graviational effects in a vacuum, and I would think acceleration is different because they're both in different mediums.

• Physics - ,

Both are wrong. In Newton's gravitational equation, is velocity of an object a consideration? Is air friction or vacumn in the equation?

• Physics - ,

Well for the first one, if its at peak of it's flight, the speed would be zero. Would the answer be B because the gravity is always constant?

and for the second one, would be answr be B then? I'm thinking that there are gravitational effects occur anywhere, like the sun's gravitational pull. The acceleration should be different due to air resistance.

• Physics - ,

yes.

• Physics - ,

Yay thanks