Newton's Laws and Free Body Diagrams

free body diagram

A diagram of force vector arrows that indicates the direction and magnitude of all forces acting on an object or system

normal force

A force applied by a surface that is perpendicular to that surface

tension force

A pulling force

A rope and pulley system is attached to a box (see below). A student pulls on the rope causing the box to accelerate upwards. When drawing the free body diagram for the box, the tension force should be directed:

straight up

A student stands on a motionless box. When drawing the free body diagram for the box, the normal force vector arrow should be drawn ______ to the gravity vector arrow.

the same size as

force

A push or a pull

friction force

A rubbing force between the surfaces of two objects

Newton's First Law

If the forces that act on an object cancel each other out then the motion will be constant velocity - this also includes a constant velocity of zero

Newton's second law

If the forces that act on an object don't cancel each other out then the object will accelerate - the object will either speed up or slow down

According to the diagram shown below, the object is:

accelerating to the right

A baseball is thrown across a field. At a point when the ball has reached its maximum height along its trajectory, the forces that should be included on a free body diagram are:

gravity

A ball falls through the air at terminal velocity. Which of the following are forces that should be included in a free body diagram? (select all that apply)

gravity air resistance

brick moves across a rough surface at constant velocity. Which of the following are forces that should be included in a free body diagram?

gravity, friction and applied force

If the forces acting on an object cancel out, the object's motion can be: (select all that apply)

moving at a constant speed standing still

An elevator moves downwards at a constant speed. When drawing the free body diagram for this motion:

the upwards tension force should be drawn the same length as the downwards gravity force

A baseball is thrown to the right. The constant velocity horizontal component of its projectile motion can be explained by drawing the free body diagram so that:

there are no forces to the left or right

A box sits motionless on a ramp as shown below. The vector arrow for the normal force of the ramp acting on the box will be directed:

up and to the left