Answer:
42 km/h was the average speed of the car for its three-hour trip.
Explanation:
Diameter of the car wheel = d = 0.4 m
Radius of the car wheel = r = 0.5 d = 0.5 × 0.4 m =0.2 m
Distance covered in 1 complete revolution = 
Distance covered in 100,000 complete revolution,D = 
1 m = 0.001 km
125,663.71 m = 125,663.71 × 0.001 km = 125.66371 km
Time taken to complete 100,000 revolution by a wheel = t = 3 hours
Speed of car : S
42 km/h was the average speed of the car for its three-hour trip.
Answer:
G M m / R^2 = m v^2 / R gravitational force = centripetal force
G M = v^2 R = constant
As v increases R will must decrease
Take the moon as an example
S = 2 pi R where R is about 240,000 miles for one orbit
S / 1 day = 54,000 miles/day for a 28 day circuit
S / 1 hr = 54000 / 24 = 2200 mph which is much less than a satellite in orbit
Mass of the block = 1.4 kg
Weight of the block = mg = 1.4 × 9.8 = 13.72 N
Normal force from the surface (N) = 13.72 N
Acceleration = 1.25 m/s^2
Let the coefficient of kinetic friction be μ
Friction force = μN
F(net) = ma
μmg = ma
μg = a
μ = 
μ = 
μ = 0.1275
Hence, the coefficient of kinetic friction is: μ = 0.1275
The horizontal force : f = k*N
k- coefficient of friction
k = f /N
N = m * g = 45 kg * 9.81 m/s² = 441.45 N
k = 25 N : 441.45 N = 0.057
Answer C) 0.057
