A 1.5 kilogram cart initially moves at 2.0 meters per second. It is brought to rest by a constant net forcé in 3.0 second. What is the magnitude of the net force ?
We know the mass = 1.5 kilogram, but we need to calculate the acceleration.
Acceleration = (change in speed) / (time for the change)
Change in speed = (ending speed) minus (beginning speed)
= ( 0 ) - ( 2 m/s ) = -2 m/s
Acceleration = (change in speed) / (time for the change)
= ( -2 m/s ) / (3 sec)
= - 2/3 m/s² .
Finally ... Net force = (mass) x (acceleration)
= (1.5 kilogram) x ( - 2/3 m/s²)
= ( - 3/2 x 2/3 ) (kg-m/s²)
= - 1 newton .
The negative sign on the force means the force is applied opposite to the direction the cart is moving. That gives negative acceleration (slowing down), and the cart eventually stops.
