Introduction to Forces

A pressing force directed straight out of a surface

• normal

• friction

• tension

• gravitational

Answer explanation

"Normal" is a mathy way of saying "perpendicular"

An attractive force between two masses

• normal

• friction

• tension

• gravitational

Answer explanation

Gravity only becomes strong enough to notice when the mass is very big, like the Earth.

A force that either prevents sliding or slows something down that's already sliding

• normal

• friction

• tension

• gravitational

Answer explanation

"static" friction prevents sliding

"kinetic" friction slows down sliding

A pulling force that is transferred through a solid object like a rope or a chain

• normal

• friction

• tension

• gravitational

Answer explanation

Tension force is always directed along the rope or chain

When the forces on an object are balanced,

• it must be stationary

• it must be going a constant velocity

• it must be accelerating

Answer explanation

A constant velocity of zero is still a constant velocity!

When the forces on an object are unbalanced,

• it must be stationary

• it must be going a constant velocity

• it must be accelerating

Answer explanation

A constant velocity of zero is still a constant velocity!

A dog is sliding to the left at a constant velocity. What can you say about the balance of forces on it?

• they are balanced

• they are unbalanced

• we can't say

A baseball player is slowing down while sliding to the right. What can you say about the forces on him?

• they are balanced

• there is a net force to the left

• there is a net force to the right

• we can't say

This is a force diagram for a sled. How could it be moving? (choose all that apply)

• sitting still

• constant velocity to the right

• constant velocity to the left

• accelerating up

• accelerating down

This is a force diagram for a sled. How could it be moving? (choose all that apply)

• sitting still

• constant velocity to the right

• constant velocity to the left

• accelerating up

• accelerating down