Shaine is doing an experiment for science class . He wants to know whether or not the type of surface on a ramp affects the amount of time it takes a toy car to reach the bottom . He creates three ramps of exactly the same length . For each ramp , he places one end on a stack of five books and one end on the top of a desk . One ramp has a sand paper surface , one has a plastic surface , and one has a wooden surface . He lets the toy car roll down each ramp , letting go from the exact same point each time . Shaine uses the same toy car on each ramp . He times how long it takes for the car to reach the bottom of each type of ramp .

What are the constants ? What are the variables that stay the same?
A: surface of ramp
B: distance the car travels/lenght of ramp
C:time
D: time of toy car

what is the independent variable?
A: surface of ramp
B: distance the car travels/lenght of ramp
C:time
D: time of toy car

what is the dependent variable?
A: surface of ramp
B: distance the car travels/lenght of ramp
C:time
D: time of toy car

what is the control group?
A: sand paper surface ramp
B: wooden surface ramp
C: plastic surface of ramp​​