Centripetal Acceleration Printer Friendly Version
Newton's 2nd law, a = net F / m, tells us that net force and its corresponding acceleration are always in the same direction. Remember that both force and acceleration are vector quantities. But force and acceleration are not always in the direction of velocity, another vector quantity.

Refer to the following information for the next three questions.

You're in a car at a traffic light. The light turns green and the driver "steps on the gas."
Your body lurches

The car accelerates

The force on the car acts

 The sketch shows the top view of the car. Note the directions of the velocity and acceleration vectors
Refer to the following information for the next three questions.

You're driving along and approach a stop sign. The driver steps on the brakes.
Your body lurches

The car accelerates

The force on the car acts

 The sketch shows the top view of the car. Draw vectors for velocity and acceleration.
Refer to the following information for the next three questions.

You continue driving, and round a sharp curve to the left at constant speed.
Your body lurches

The car accelerated

The force on the car acts

 The sketch shows the top view of the car. Draw vectors for velocity and acceleration.
In general, the directions of the lurch and the acceleration, and therefore the firections of the lurch and the force, are

Refer to the following information for the next two questions.

The whirling stone's direction of motion keeps changing.
If it moves faster, its direction changes

This indicates that as speed increases, acceleration

Refer to the following information for the next two questions.

Consider whirling the stone on a shorter string-that is, of smaller radius.
For a given speed, the rate that the stone changes direction is

This indicates that as the radius decreases, acceleration

 Paul G. HewittCopyright © 1984-2005All rights reserved.Used with written permission. PhysicsLABHTML conversionCopyright © 1997-2024Catharine H. ColwellAll rights reserved.Mainland High SchoolDaytona Beach, FL 32114