Question

Sam, whose mass is 60 Kg, is riding on a 5.0 kg sled initially traveling at 8.0 m/s. He

Answer 1

Answer:  130 newtons

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Explanation:

We'll need the acceleration first.

• The initial speed (let's call that Vi) is 8.0 m/s
• The final speed (Vf) is 0 m/s since Sam comes to a complete stop at the end.
• This happens over a duration of t = 4.0 seconds

The acceleration is equal to the change in speed over change in time

a = acceleration

a = (change in speed)/(change in time)

a = (Vf - Vi)/(4 seconds)

a = (0 - 8.0)/4

a = -8/4

a = -2

The acceleration is -2 m/s^2, meaning that Sam slows down by 2 m/s every second. Negative accelerations are often associated with slowing down. The term "deceleration" can be used here.

Here's a further break down of Sam's speeds at the four points of interest

• At 0 seconds, he's going 8 m/s
• At the 1 second mark, he's slowing down to 8-2 = 6 m/s
• At the 2 second mark, he's now at 6-2 = 4 m/s
• At the 3 second mark, he's at 4-2 = 2 m/s
• Finally, at the 4 second mark, he's at 2-2 = 0 m/s

Next, we'll apply Newton's Second Law of motion

F = m*a

where,

• F = force applied
• m = mass
• a = acceleration

We just found the acceleration, and the mass is fairly easy as all we need to do is add Sam's mass with the sled's mass to get 60+5.0 = 65 kg

So the force applied must be:

F = m*a

F = 65*(-2)

F = -130 newtons

This force is negative to indicate it's pushing against the sled's momentum to slow Sam down.

The magnitude of this force is |F| = |-130| = 130 newtons