Answer to Question #148989 in Mechanics | Relativity for drew

Question

For part 3 of 3, just enter magnitude (positve number) A 1720 kg car has a speed of 10.3 m/s when it hits a tree. The tree doesn’t move and the car comes to rest. Find the change in kinetic energy of the car. Answer in units of J. 008 (part 2 of 3) 10.0 points Find the amount of work done by the car as its front is pushed in. Answer in units of J. 009 (part 3 of 3) 10.0 points Find the magnitude of the force that pushed the front of the car in by 50 cm . Answer in units of N.

Answer 1

mass of the car, $m = 1720 kg$

initial speed, $u = 10.3 m/s$

When it hit tree and comes to rest, then velocity of the car, $v = 0 m/s$

Change in kinetic energy, $\Delta K.E. = \frac{1}{2}mu^2-\frac{1}{2}mv^2 = \frac{1}{2}mu^2 = \frac{1}{2}\times 1720\times (10.3)^2 = 91.24\times 10^3 J$

Work done by the car is equal to change in kinetic energy,

$W = \Delta K.E. = 91.24 \times 10^3 J$

Force is find by the formula,

$W = Fd$

where d is the displacement (i.e. push)

$F = \frac{W}{d} = \frac{91.24 \times 10^3 }{0.5} = 182.5 \times 10^3 N$