Suppose an automobile has a kinetic energy of 2800J.?

Question

When it moves three times the speed, what will be the kinetic energy?

Answer 1

k - Kinetic energy.
m - Mass.
v - Velocity.

k = ½ m v² (Taken a unit speed of one).
2800 J = ½ m(1)²
5600 = m

If the speed is three times, then:
k = ½ m v²
k = ½ (5600) (3)²
k = 25,200 J

Answer 2

Let v be the speed of the object. In that case, it's kinetic energy (call it a) is:

a = 0.5 * m * v^2

If you replace v by 3v, then the new kinetic energy (call it b) is:

b = 0.5 * m * (3v)^2 = 0.5 * m * 9 * v^2 = 9 * 0.5*m*v^2 = 9*a

Thus, b = 9*a.

You were given a=2800J, so find b.

Answer 3

kinetic energy(k) is directly proportional to velocity square(considering that mass remains constant)
therefore the new k will be 9 times the old one

Answer 4

2800J=(1/2)(m)(v^2
assume mass(m= const.)
then solve for v.
once you find v, do times 3 which should give you the answer.
if assume that mass is not changin then that should solve your problem.
otherwise, it maybe a little bit complicated if you have a variable mass in the object.
hope it helps.