Force Fundamentals
What is a force?
A push or a pull
Equal forces that do not change an object’s motion are called what?
Balanced forces
What force resists motion when two surfaces touch?
Friction
What tool measures the amount of force needed to move an object?
A spring scale
What variable does the scientist purposely change?
Independent variable
Why should scientists complete several trials?
To make the results more reliable and accurate
A student wants to investigate how a wagon’s mass affects the force needed to pull it. Describe the independent variable, dependent variable, and two constants.
What unit is used to measure force?
Newtons (N)
A student sits still on a bench. Are the forces balanced or unbalanced?
Balanced
Which usually creates more friction: a rough surface or a smooth surface?
A rough surface
What force pulls an object down a ramp?
Gravity
What variable does the scientist measure or observe?
Dependent variable
Students test how a block’s mass affects the force needed to move it, but they pull each block across a different surface. What should they change?
Pull every block across the same surface.
A student wants to determine whether the mass of a toy car affects how far it travels down a ramp. Identify the independent variable, dependent variable, and two constants.
Independent variable: mass of the car
Dependent variable: distance traveled
Constants: ramp height, starting point, ramp surface, car type, or release method
A shopping cart is sitting still. A person pushes it toward the left. What will happen?
The cart will begin moving toward the left
A child swings back and forth, changing speed and direction. Are the forces balanced or unbalanced?
Unbalanced
Students roll identical toy cars across tile, carpet, and sandpaper. What are they testing?
How different surfaces or friction affect the cars’ motion
A ball is released from a short ramp and then a taller ramp. From which ramp will it likely travel faster and farther?
The taller ramp
What are the variables kept the same during an investigation called?
Constants or controlled variables
Students compare the strength of three magnets but place each magnet at a different distance from the paper clips. What should they fix?
Place every magnet the same distance from the paper clips
A soccer ball and a bowling ball are kicked with the same amount of force. Which ball will move more easily, and why?
The soccer ball because it has less mass
One person pushes a box right with 120 N while another pushes left with 80 N. What is the net force and in what direction will it move?
40 N to the right
Students want to test the effects of friction. Should they roll identical balls across different surfaces or drop different balls from different heights?
Roll identical balls across different surfaces
A student pulls a heavy load up a ramp. What ramp change would reduce the force needed?
Decrease the ramp’s height or steepness
A student changes how forcefully a ball is thrown and measures the splash height. Identify the independent and dependent variables.
Independent: throwing force; dependent: splash height
An inventor compares the strength of different materials by dropping the same ball from the same height. However, each material has a different thickness. How should she improve the investigation?
Test different materials that all have the same thickness.
The same ball is dropped onto clay from two different heights. Why does the higher drop make a deeper dent?
The ball hits the clay with greater force
(Side A) Three equally strong students pull against (Side B) two equally strong students in tug-of-war. Which side should win, and why?
Side A with three students because it applies more total force, creating unbalanced forces
A toy car travels 32 cm on sandpaper, 48 cm on cardboard, and 57 cm on wax paper. Would it likely travel more or less than 57 cm on smooth ice? Explain.
More than 57 cm because smooth ice produces less friction
Students launch spheres of different masses from the same spring. What tool should measure the results, and what should it measure?
A meterstick measuring the height or distance each sphere travels
Students test how the width of an elastic strip affects how far it stretches. What should they change, measure, and keep the same?
Change the width, measure the stretch, and keep the length and attached mass the same
Students use the same toy car, ramp, and starting point but change the surface beneath the car. What are the independent variable, dependent variable, and the constant/controls?
Independent: surface; dependent: distance traveled; constant: car, ramp height, or starting point