Kinetic energy problem.... please help...?

Question

A sphere with heft 4 kg, is thrown horizontally with a velocity 15m/s. Find the kinetic energy in the end of the third second.

Answer: 2.18 kJ

Answer 1

We assume that it is thrown at a sufficient elevation that it is still in mid-air three seconds later. We need to find the vertical velocity after three seconds, due to gravitational acceleration, and then use that with the horizontal velocity, assumed to be constant because we neglect air resistance, to find the total velocity. We need total velocity because kinetic energy is KE = 0.5*mv^2.

Vertical velocity due to gravitational acceleration is v_y = gt, where g is gravitational acceleration, 9.8 m/s^2, and t is elapsed time, which was given as 3 s. Given velocity components v_x and v_y, the total velocity is sqrt((v_x)^2 + (v_y)^2). You just calculated v_y, and v_x is unchanged from the initial 15 m/s. So now you can calculate KE = 0.5*mv^2, where have calculated v and m was given as 4 kg.

Answer 2

Its pretty simple:

See, first the sphere moves horizontally so K.E1 = 1/2 M V^2
so we get K.E1 = 0.5 * 4 * 225 = 450
But there's also force due to gravity. As there is no initial downward or upward throw the vertical velocity is 0.
v = u + at; => v = 0 + 9.8 * 3
v = 29.4
Now plugging this into K.E2 = 0.5 * 4 * 29.4^2 = 1728.72

Now adding both the K.E's , K.E = K.E1 + K.E2 = 2178.72 which is 2.178 kJ :)

Answer 3

The vertical acceleration downwards due to gravity is 9.8m/s². After 3 seconds the vertical velocity will be 29.4m/s¹ (9.8 x 3).
To work out its velocity when combining vertical and horizontal counterparts we use pythatoras' theorum. √(15² + 29.4²) = 33m/s¹
Kinetic energy is given by 0.5mv²
so E = 0.5 x 4 x 33²
E = 2178 J
E = 2.178 kJ

Answer 4

as there is no horizontal force on the sphere, itshorizontal velocity remains constant, after 3 secondsitsvelocity =15m/s
its vertical velocity =0+9.8*3=29.4m/s
then its kinetic energy=(1/2)mv^2= m/2(15^2+29.4^2
2(225+864.34)=2178.68joules=2.18k joules

Answer 5

Is the skier shifting or merely status at a element 15.9 M down the slope? If he's merely status nevertheless, the respond is 0, so I certainly have solved for one severe. We now comprehend the respond won't be able to be under 0. additionally, how lots friction is there between the skier and his lady buddy? How tall is the skier? the place is the ski slope? the better the altitude, the less warm that's sometimes, watching the variety! Is the skier donning a sort of quite cool slick racing clothing or is he/she donning baggies? Is the skier a he or a she or is it a he-she? those issues all count in actual existence once you bypass snowboarding. My father's lady buddy licked my thigh as quickly as!!

Answer 6

I also agree with both of the above answers the 2nd is the easiest to understand as it is showing the workign for you.