Answer: The time of contact will be 0.006 seconds.
Explanation:
An impulse of a force is the product of average force and the time interval when the force acts.
Mathematically,

Where,
J = impulse = 3.6 Ns
F = Force = 600N
= Time = ?s
Putting the values in above equation, we get:

t = 0.006 seconds
Hence, the time of contact will be 0.006 seconds.
The time taken by the sled to reach 45 m to the bottom is 4.24 s.
The sled's initial velocity <em>u</em> is zero. It has an acceleration <em>a</em> of a value 5 m/s² down the hill and it travels a distance <em>s</em> equal to 45 m down the hill.
Use the equation of motion,

Substitute 0 m/s for u and rewrite the equation for t.

The sled takes a time of 4.24 s to reach the bottom of the hill
Answer:
15.7 N
Explanation:
Draw a free body diagram. The block has four forces acting on it. Gravity pulling down, normal force pushing perpendicular to the plane, friction pointing up the plane, and applied force F pushing up the plane.
Sum of the forces normal to the plane:
∑F = ma
N − mg cos θ = 0
N = mg cos θ
Sum of the forces parallel to the plane:
∑F = ma
Nμ + F − mg sin θ = 0
F = mg sin θ − Nμ
Substituting:
F = mg sin θ − mgμ cos θ
F = mg (sin θ − μ cos θ)
Given mg = 87.0 N, θ = 24.1°, and μ = 0.25 (because the block is not moving):
F = 87.0 N (sin 24.1° − 0.25 cos 24.1°)
F = 15.7 N