Question

1. Which has the greater kinetic energy, a heavy truck at rest or a moving roller skate?

a. none of above

b. heavy truck at rest

c. the roller skate at rest

d. The kinetic energies are equal.

2. If a sports car with a mass of 2000 kg travels down the road with a speed of 10 m/s, its kinetic energy is _______________ kg (m/s)2

a. 80000

b. 16000

c. 8000

d. 100000

e.none of above

3. A sports car with a mass of 1000 kg travels down the road with a speed of 20 m/s. Which is larger, its momentum or its kinetic energy?

a. momentum

b. They are equal.

c. none of above

d. kinetic energy

e. The kinetic energy is always greater than the momentum

4. The kinetic energy of an object moving in a circle at a constant speed is

a. equal to one half of the mass times linear speed's square

b. equal to the force times the time for one revolution

c. continually changing as the force changes direction

d. changing all the time

e. none of above

Answer 1

KE =0.5*m*v^2

rest truck v = 0 so KE = 0

a moving roller skate has more KE but I see it is not in any options so answer wud be  none of the above

2) KE = 0.5*m*v^2 = 0.5*2000*10^2 = 100000

d. 100000

3) first of all they can't be compared because one is energy and other is none energy

momentum = m*v= 1000*20 =20000

KE = 1/2*m*v^2 = 0.5*1000*20^2 =200000

so KE > momentum

d. kinetic energy

4)

Option D is right when circular motion in vertical plane

as K.E gets converted into potential energy and potential energy into kinetic energy.

KE is maximum at lowest point of circle and minimum at top point on circle.