physics question on motion in one dimension

Question

 is motion of a ball on a smooth surface an example of uniform velocity?  is motion of a ball on a rough surface an example of variable velocity? is a car moving on a straight path an example of uniform speed? is a body pushing a car an example of force as per Newtons first law of motion.is a car moving on a criss cross road an example of variable acceleration?        

Answer 1

Lots of questions here.  Let's start with Newton's First Law of Motion: a) A body at rest will remain at rest unless acted upon by a force; b) A body with a uniform velocity (straight line, constant speed) will maintain that uniform velocity unless acted upon by a force.  Now let's evaluate your problems.

 

a) is motion of a ball on a smooth surface an example of uniform velocity?  If the surface is flat so gravity is not acting on the ball's motion, then yes the ball will follow Newton's First Law and maintain its uniform motion.  (The smooth surface means that we can ignore the force of friction)

 

b) is motion of a ball on a rough surface an example of variable velocity?  A velocity is variable if it changes speed or direction.  On a rough surface, the ball will get knocked around a bit, both up and down and left and right.  So the changes in speed and direction produce a variable velocity.

 

c) is a car moving on a straight path an example of uniform speed?  A uniform velocity is defined as motion in a straight line at a constant speed.  Moving in a straight line does not guarantee that the speed is constant.  For example, a drag race car moves in a straight line but its speed in constantly increasing.

 

d) is a body pushing a car an example of force as per Newtons first law of motion?  Suppose the car is at rest.  Newton's First Law says it will remain at rest unless a force acts on it.  When you push on the car, it starts to move; it is no longer at rest.  So yes, pushing on a car is a force.

 

e) is a car moving on a criss-cross road an example of variable acceleration? I'm guessing that a "criss-cross" road is a road with lots of curves on it.  Remember, velocity is both speed and direction.  Acceleration is a change in velocity; that is it is a change in either the speed or the direction.  Since the car is going around many curves, it is changing directions.  If you turn one way, you accelerate in that direction.  If you then turn the other way, you accelerate in a different direction.  So, yes, driving on a criss-cross road is an example of both variable velocity and variable acceleration.

 

Hope that helps.

Answer 2

Answer is Yes to all questions.