Question

An athlete on a sled is moving with a speed of 3.0 m/s across a pond covered with ice. If the total mass of the sled-athlete system is 95.0 kg, what magnitude of the average force is required to bring the sled to rest in 15.0 s

Answer 1

F = –19N

Step-by-step explanation:

u = 3.0m/s = initial velocity, m = 95.0kg, v = 0m/s = final velocity of the sled because it comes to rest.

Δt = 15.0s.

The average force required to bring the sled to rest is equal to the change in momentum of the sled. From Newton's second law,

F = m(v-u)/Δt = 95×(0 – 3)/15 = –19N

F = –19N

The force is negative because it is against the direction of the initial motion or it is so because it is the force applied to bring sled to rest (to decelerate its motion)

Answer 2

Given Information:

Mass = m = 95 kg

Initial velocity = v₁ = 0 m/s

Final velocity = v₂ = 3 m/s

time = t = 15 seconds

Required Information:

magnitude of average force = ?

Answer:

magnitude of average force = 19 N

Explanation:

From the Newton's second law of motion

F = ma

From the kinematics equations,

v₂ = v₁ + at

at = v₂ - v₁

a = (v₂ - v₁)/t

a = (3 - 0)/15

a = 0.2 m/s²

F = 95*0.2

F = 19 N

Therefore, the magnitude of the average force required to bring the sled to rest is 19 N.