A boy is exerting a force of 70 N at a 50-degree angle on a lawnmower. He is accelerating at 1.8 m/s2. Round the answers to the nearest whole number. What is the mass of the lawnmower?
What is the normal force exerted on the lawnmower?

The lawnmower accelerates in the positive horizontal direction, so that the net horizontal force is, by Newton's second law,

(70 N) cos(-50°) = m (1.8 m/s²)

where m is the mass of the lawnmower. Solve for m :

m = ((70 N) cos(-50°)) / (1.8 m/s²)

m ≈ 25 kg

The lawnmower presumably doesn't get lifted off the ground, so that the net vertical force is 0. If n is the magnitude of the normal force, then by Newton's second law,

n - m g + (70 N) sin(-50°) = 0

n = m g + (70 N) sin(50°)

n = (25 kg) (9.8 m/s²) + (70 N) sin(50°)

n ≈ 300 N

3. dark matter

empty space could also be a simple vacuum