in the figures there is shown a vehicle 10 which has a body shell 12 mounted onto a chassis 14 having front wheels collectively identified by the numeral 16 and rear wheels collectively identified by the numeral 18 . on top of the body shell 12 is an activation button 20 . in operation , the activation button 20 is depressed inwardly into the body shell 12 . the vehicle 10 is then propelled across a support surface by giving the vehicle a push or shove or the like . as the vehicle rolls across the support surface after a predetermined distance , as hereinafter explained , the vehicle forceably lifts or jumps from the support surface and becomes airborne for a sort period of time and then returns to the support surface . in one embodiment of the invention shown in fig1 through 4 certain mechanisms within the interior of the toy are so located that the toy essentially jumps upwardly and then lands back down on all four of its wheels so that it can continue rolling . in other embodiments of the invention , as hereinafter explained , certain of the components in the interior of the toy can be repositioned to different locations such that the toy will perform different motions such as doing a flip or the like . referring now to fig2 the body shell 12 has been removed from the toy vehicle 10 to illustrate certain of the internal components . a u - shaped member 22 projects upwardly and across the top of the chassis 14 . it includes an opening 24 in its top surface which serves as a guide or pilot hole for a shaft 26 which is attached to the bottom of the activation button 20 . located on the lower end of the shaft 26 is an inertial mass element 28 . the element 28 is preferredly formed of a metal or other dense material such that it has a substantial mass compared to the remainder of the chassis 14 and body shell 12 which are preferredly formed of a plastic or the like material . a strong compression spring 30 is located within a channel 32 within the mass element 28 . the spring 30 is compressed between the bottom wall 34 of the chassis 14 and the bottom of the inverted channel 32 . the spring 30 biases or urges the mass element 28 upwardly toward the top of the u - shaped member 22 . a retaining member 36 is pivoted via a pin 38 to the underside of the u - shaped member 22 . the retaining member 36 essentially pivots horizontally toward and away from the shaft 26 . the mass element 28 includes a shoulder 40 which can catch underneath the retaining member 36 when the retaining member 36 is pivoted towards the shaft 26 . when the retaining member 36 is pivoted away from the shaft 26 it clears the shoulder and allows the mass element 28 to be lifted upwardly by the spring 30 . a hairpin spring 42 is connected at one of its ends to the retaining member 36 and at the other of its ends to the u - shaped member 22 . it is compressed so that the spring 42 urges the retaining member 36 toward the shaft 26 . because of this when the mass element 28 is pressed downwardly by pushing down on the activation button 20 compressing the spring 30 , the retaining member 36 swings over toward the shaft 26 to lock on top of the shoulder 40 to hold the mass element 28 downwardly with the spring 30 in a compressed or biased position . a drum 44 having a crank pin 46 on its upper surface is rotatably mounted via pin 48 to the bottom wall 34 of the chassis 14 . the drum 44 includes a spur gear 50 along its lower periphery . the drum 44 and the spur gear 50 are formed as an integral unit such that the crank pin 46 rotates with respect to rotation of the spur gear 50 . a spring 52 connects between the crank pin 46 and a tab 54 which is formed as a part of the chassis 14 . this essentially biases the drum to the position shown in fig2 . the drum 44 has a hollow interior . to receive a compression , spring 56 fits underneath the drum 44 and contacts the bottom wall 34 of the chassis 14 so as to bias the drum 44 upwardly until it engages the head of the pin 48 . the mass element 28 includes an extension 58 on its forward edge which projects over the edge of the drum 44 . when the activation button 20 is depressed the extension 58 contacts the drum 44 and depresses it downwardly against the bias of the spring 56 . the front wheels 16 are mounted about an axle 60 which includes a worm gear 62 fixedly located thereon . the axle 60 fits into elongated slots 64 on the left and right hand side of the chassis 14 which allows the axle 60 to move upwardly and downwardly a small increment of distance with respect to the chassis 14 . likewise the rear wheels 18 are mounted to an axle 66 which are also located in slots 68 such that the rear wheels and their axles 66 can also move upwardly and downwardly through a short increment of distance . when the vehicle 10 is placed on a support surface the weight of the vehicle 10 causes the chassis 14 to move downwardly with respect to the axle 60 and 66 such that they are located in the top of their respective slots 64 and 68 . if the activation button 20 is depressed the inertial mass element 28 is depressed and its extension 58 contacts the top of the drum 44 pushing the drum 44 downwardly such that the spur gear 50 engages the worm gear 62 on the axle 60 . rotation of the axle 60 in response to rotation of wheels 16 rotates the worm gear 62 which in turn rotates the spur gear 50 . the rotation of the spur gear 50 rotates the drum 44 clockwise as is seen in fig4 . as the drum 44 rotates when it nears the position as shown in fig4 the crank pin 46 contacts the retaining member 36 and further rotation of the drum 44 moves the retaining member 36 such that it pivots about the pin 38 and compresses the hairpin spring 42 . this moves the retaining member 36 in a direction away from the shaft 26 such that eventually it is moved sideways off of shoulder 40 allowing the inertial mass element 28 to be forcefully accelerated upwardly by the spring 30 . as the mass element 28 moves upwardly it eventually contacts the underside of the u - shaped member 22 and the momentum of the mass element 28 under the acceleration imparted to it by the spring 30 is transferred to the member 22 which in turn transfers it to the chassis 14 and the remainder of the vehicle 10 . the vehicle 10 then is accelerated upwardly by the force imparted to it by the movement of the mass element 28 . when the mass element 28 moves upwardly under the force of the spring 30 its extension 58 moves upwardly with respect to the drum 44 allowing the spring 56 to move the drum upwardly until the spur gear 50 on the drum 44 is no longer in a position to contact the worm gear 62 on the axle 60 . when the vehicle 10 descends downwardly to the support surface the axle 60 is free to rotate and any forward momentum still imparted into the vehicle 10 by its initial forward push continues to propel the vehicle 10 forward . as such the vehicle 10 is first driven forward , then it jumps or hops and becomes airborne and when it lands it continues in its forward movement until all of its momentum is lost . the spring 52 repositions the drum 44 into the position essentially seen in fig2 after each mode of operation . further , if the activation button 20 is depressed such that the inertial mass element 20 becomes locked under the retaining member 36 it will be retained in this position until the retaining member 36 is moved by the crank pin 46 . if the vehicle 10 is only moved forward a short increment , the interaction of the worm gear 62 with the spur gear 50 will only partially rotate the drum 44 from the position seen in fig2 to the position seen in fig4 . if the vehicle is then lifted from the support surface the front axle 60 will drop which disengages the worm gear 62 from the spur gear 50 and allows the drum 44 to rotate under the influence of the spring 52 . whether or not the drum 44 rotates counterclockwise or clockwise depends upon the exact location of the crank pin 46 . if the crank pin 46 is off center to one side or the other from the line passing through the pin 48 and the spring 56 it will rotate to one side or the other depending upon which side it is on . as such the operator of the vehicle 10 will not know whether or not the drum 44 has rotated back to its initial position or whether it has come to rest against the retaining member 36 . the spring 52 is normally chosen to be of such a strength that it in itself is not capable of moving the retaining member 36 but requires rotation of the drum 44 by the axle 60 in order to move the retaining member 36 against the bias of the hairpin spring 42 . as such the operator of the toy can physically move the vehicle 10 forward an increment and then give it a small shove . if the drum 44 had returned to its starting position as in fig2 the vehicle must travel a longer distance before it jumps . if the drum had rotated under the influence of spring 52 to the position shown in fig4 it will execute its jumping motion almost immediately upon initialization of its forward rolling motion . when the drum 44 is in its upward position against the head of its pin 46 the spur gear 50 is lifted upwardly out of range of contact with the worm gear 62 . as such in this mode of operation the vehicle 10 is freewheeling and can be played with in a normal manner like any freewheeling vehicle . it is only when the drum 44 is depressed downwardly by the extension 58 of the inertial mass element 28 and the worm gear 62 is lifted upwardly when the front axle 60 is in the upward end of travel within the slots 64 that the worm gear 62 can engage the spur gear 50 . the remainder of the time the vehicle is free wheeling . a further embodiment of the toy is shown in fig5 . in this embodiment of the toy the inertial mass element 70 is moved forward such that it is placed just slightly behind the front axle 72 . the retaining member 74 is pivotally mounted near the front of the vehicle and in place of a drum 44 a large spur gear 76 is utilized which incorporates a cam 78 on its surface . a spring 80 is utilized to position the spur gear 76 and cam 78 as per the spring 52 . further a spring 82 is utilized to position the retaining member 74 over the shoulder 84 of the inertial mass member 70 . a worm gear 86 is located on the rear axle 88 to rotate the spur gear 76 counterclockwise . this causes the cam 78 to engage the end of the retaining member 74 to rotate it such that the inertial mass element 70 is free to be accelerated upwardly by a spring 90 located between it and the chassis 14 . because the inertial mass element 70 is located near the front of the vehicle as opposed to the center position of the previously described inertial mass element 28 within the vehicle 10 , when the vehicle of fig5 is operated , upon acceleration of the inertial mass element 70 upwardly against the chassis of the vehicle of fig5 the front end of the vehicle will be given a greater momentum than the back end of the vehicle such that the vehicle will do a flip instead of a straight upward jump . it is obvious that in place of locating an inertial mass element 28 in the center of the vehicle as per the first embodiment or the inertial mass element 70 in the front of the vehicle as per the embodiment in fig5 it could be placed near the rear of the vehicle or to one side or the other with a resulting movement of the vehicle corresponding to placement of the inertial mass element .