Purpose: To determine whether an object that rolls down a ramp has the same range as an object which slides down a ramp.

 

Equipment needed:  Each group needs: ramp, steel ball, target paper, meter stick, plumb line

 

Resource Lessons: 2D projectiles (horizontal release), Conservation of Energy.

 

 

Remember that when analyzing two-dimensional projectile motion, the horizontal and vertical motions are independent of each other. Horizontally, projectiles in freefall travel at a constant velocity; while vertically, they experience uniform acceleration resulting in a classic parabolic trajectory. Our secret to working projectile problems was to build a chart in which we delineated the Horizontal | Vertical properties in each situation.

 

 

 

Horizontally, the only equation available to us was R = v_Ht, where v_H represents the projectile's constant horizontal velocity. Vertically, in the above illustration, the projectile's initial velocity equaled zero, since it was launched straight forward.  Usually, in this situation, we let v_o = 0, a = -9.8 m/sec², and s = -h and then used the kinematics equation  s = v_ot + ½at² to solve for the time that the projectile spent in the air.

 

 

 

Your  goal in this experiment is to predict where a steel ball will land on the floor after having rolled down an incline plane. The final test of your measurements and computations will be to position a bull's-eye on the floor so that the ball lands in its center circle on the first attempt. Make sure that ALL measurements and calculations are reported with three significant figures.

 

 

 

Step 1: Assemble your ramp. Make it as sturdy as possible so the steel ball rolls smoothly and consistently. The ramp should not sway or bend. Since the ball must leave the table horizontally, make sure that the horizontal part of the ramp is level with the surface of the table. The vertical height, h, of the ramp should be no less than 7 cm.   Step 2: Calculate the ball's horizontal velocity at the base of the ramp using conservation of energy principles. At the top of the ramp, if the ball is released from rest, it will only have potential energy, PE, which equals the product of its mass (in kilograms) times the acceleration due to gravity (9.8 m/sec2) and its height (in meters) above an arbitrary reference line. At the base of the ramp, the ball has translational kinetic energy, KE, which equals half the product of its mass (in kilograms) times the square of its velocity (in m/sec).

PEtop = KEbase mgh =  ½mv2 2mgh =  mv2 √2gh =  v

 

This velocity at the base of the incline will remain the ball's horizontal velocity when it leaves the table. Remember that you will need to consistently release the ball from the same height on the ramp as well as not put any pressure against the ramp that might result in it "springing" forward when the ball is released.

 

 

 

 

 

To continue with your analysis, you must obtain the mass of your marble.

 

 

A form of energy that all rotating objects possess is called rotational kinetic energy. The same way that massive objects resist translational acceleration, they also resist rotational acceleration. This type of resistance is known as rotational inertia and gives rise to an energy known as rotational kinetic energy.

The rotational kinetic energy of a uniform rolling sphere can be calculated using the formula

KE_rot = (1/5)mv².

 

Notice that KE_rot, as is true with all types of energies, is measured in joules.