Question

1) If the child pulls with a force of 15 N for 15.0 m , and the handle of the wagon is inclined at an angle of 25 ∘ above the horizontal, how much work does the child do on the wagon?

2) On October 9, 1992, a 27-pound meteorite struck a car in Peekskill, NY, creating a dent about 22 cm deep. If the initial speed of the meteorite was 560 m/s , what was the average force exerted on the meteorite by the car?

Answer 1

1.solution

We know work done is scalar quantity hence work done
W = F.S.cos
W = 15*15*cos25
W = 204 J

2.solution

Use the kinematic equations of motion to find the average acceleration (actually, deceleration, but that's just negative acceleration) of the meteorite, and then use Newton's Second Law, F = ma, to find the force.

We're going to need the mass in kg for this. But 1 kg = 2.2 pounds, so 27 pounds = 27/2.2 = 12.2727 kg.

Now lets's find the acceleration. We have the following information:

u = initial speed = 560 m/s
v = final speed = 0 m/s
d = distance = 0.22 m
a = acceleration = ?

v² = u² + 2ad. Since v = 0, this can be written 2ad = -u², so a = -u²/2d = -(560 m/s)²/2*0.22 m = - 7.12*10⁵ m/s²,

now F = ma = 12.2727kg* 7.12*10⁵ = 8.74*10⁶ N