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NOTE This is a multi-part question. Once an answer is submitted, you will be unable to return to this part.
A 11-kg sled sliding freely on an icy surface experiences a 4-N frictional force exerted by the Ice and an air-resistive force
of 0.6 N.
What is the net force acting on the sled?

The net force is 4.6 [N]

Explanation:

If the sled moves freely and with constant speed at that time, it is because there is no acceleration, therefore applying newton's second law of motion we can say that the sum of the forces acting on the sled is equal to zero.

The force that counteracts friction and wind must be directed in the opposite direction to these two.

- 4 - 0.6 + F = 0

F = 4.6 [N]

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s