Physics Quiz 1

A 3000-N bear grasping a vertical tree slides down at constant velocity. The friction force between the tree and the bear is

3000 N.

An 800-N man stands at rest with his weight evenly distributed on two bathroom scales. The reading on each scale is

400 N

In a dream you're in a car traveling at 50 km/h and you bump into another car traveling toward you at 48 km/h. The speed of impact is

98 km/h

In what direction does friction act?

Friction acts in a direction that opposes the motion or attempted motion of an object.

According to Galileo, how much force (directed along the surface, besides the upward force from the flat surface) is needed to keep a ball rolling on a flat surface (neglecting the effect of friction)?

No force is needed to keep the moving ball moving in the absence of friction.

Given that two forces of 10 N and 15 N act horizontally (one dimension) on an object, the net force must

be either 5 N or 25 N.

Burl and Paul on a sign-painting scaffold are in equilibrium, which means that the net upward supporting force of the vertical ropes is

equal and opposite to the combined weights of Burl, Paul, and the scaffold.

A stone is dropped off a cliff and is in free fall. Every second that the stone is falling, its acceleration _______.

is constant but its velocity is increasing

When a ball increases in speed by the same amount each second, its acceleration

is constant.

A car is traveling with constant velocity. This means that _______.

it is traveling in a straight line and its speed is not changing