Question

Can someone answer these please?

Answer 1

9.  Force = mass * acceleration.

F = ma

(8) = (1)a

8m/s^2 = a

10.  First solve for the kinetic energy of the vehicle:

Kinetic energy = (1/2)mass * velocity^2

KE = (1/2)(1200)(2)^2

KE = 2400J

Now use this value in the equation for work:

Since the car comes to a halt, the work is equal to the kinetic energy.

Work = Force * Displacement

W = Fd

(2400) = F(0.15)  Remember to convert cm to m

1.6*10^4 N = F

Answer 2

9.

The 1N = 1kg * 1 m/s^2 has no influence on the answer.

F = 8 N

m = 1 kg

a = ??

F = m * a

8N = 1 kg * a

8N/1kg = a

a = 8 m/s^2

10

This is the beginning of a 2 step process. You are back to the basic 4 equations to find the acceleration. Then you can use F = ma

Givens

m = 1200 kg

vi = 2m/s

vf = 0

d = 15 cm = 0.15 m

Formula

F = m*a

vf^2 = vi^2 + 2 * a * d

0 = 2^2 + 2 * a * 0.15,

0 = 4 + 0.3 * a

- 4 = 0.3 * a

- 4 / 0.3 = a

- 13.3333333 = a

F = m * a

F = 1200 * (- 13.3333333)

F = - 16000 N

Comment (Extremely Important)

Why aren't any of the answers minus? It is because the minus represents the amount of force needed to stop the vehicle. But the question asks you about the rock. What is the rock experiencing? The rock is opposing the 0.15 m so the force it offers is in the opposite direction to that exerted by the vehicle.