Answer to Question #98880 in Classical Mechanics for Faheem

Question

Is it true or wrong to say that an object with zero acceleration has velocity? Either yes or no explicate it with example.

Can we say that an object with zero velocity have acceleration? Either yes or no explicate it with example.

Is it wrong or correct to say that, if an object has constant acceleration, it has a constant velocity? Either yes or no explicate it with example.

Question No. 2
Estimate the soccer ball‘s speed immediately after being kicked off if its mass is 0.5Kg as shown in the given figure.

F . . . F=250N
∆x= 0.20m
F= 256N
V= ?

Answer 1

Question 1:

 An object with zero acceleration can move at a constant speed according to Newton’s first law. According to which, if the sum of forces is zero, the body moves uniformly and rectilinearly or rests.

 An object with zero speed does not have acceleration also according to Newton's first law.

 If an object has acceleration, then its speed increases with time. From this we obtain that the statement is false.

 Question 2:

 Due to the lack of a drawing, I will assume that the force acting on the ball is only gravity:

$F=m\cdot g=0,5\cdot10=5N$

$a=g=10 \frac{m}{s^2}$

$v=\sqrt{2\cdot a\cdot x} = \sqrt{2\cdot 10\cdot 0.2}= 2 \frac{m}{s}$