Question

A student is using a cart to investigate force. The student applies a pushing force to the empty cart as shown. He observes that the cart moves easily.







Next, the student adds 20 kg of mass to the cart. The student applies the same pushing force. He observes that the cart moves slower.







The following question has two parts. First, answer Part A. Then, answer Part B.



Part A:

Which graph correctly represents the relationship between force and mass on objects when the acceleration is constant?


The graph shows Force on the horizontal axis and Mass on the vertical axis. A straight line starts from the origin and points towards the top right of the graph.


The graph shows Force on the horizontal axis and Mass on the vertical axis. A straight line starts half way up the vertical axis and is parallel to the horizontal axis.


The graph shows Force on the horizontal axis and Mass on the vertical axis. A straight line starts from the top left of the vertical axis and points toward the bottom right of the graph.


The graph shows Force on the horizontal axis and Mass on the vertical axis. A straight line starts half way up the vertical axis and is parallel to the horizontal axis until about half way across the horizontal axis and then bends toward the top right of the graph.





Part B:

Based on the graph chosen in Part A, how can the student make the cart move faster when more mass is added to the cart?


by applying less force


by applying more force


by increasing the area of the cart


by decreasing the area of the cart

Answer 1

Part A: The first graph (Force on horizontal axis, Mass on vertical axis, straight line from origin to top right).
Reason: For constant acceleration F = ma, so force is directly proportional to mass (a straight line through the origin).

Part B: by applying more force.
Reason: To get a greater acceleration (move faster) with more mass you must increase the net force (F = ma).