A toy car (200 g) moves by shooting a plastic ball (50 g)
horizontally out the back. The average acceleration of the
car is 1.2 m/s
2
[E] and there is negligible friction acting on
each part of the toy. T / I C
(a) Draw an FBD for each object.
(b) Identify the action and reaction forces on each part
of the toy
(a) To draw a free body diagram (FBD) for each object, we need to represent all the forces acting on the car and the plastic ball separately.
Free body diagram for the car:
- Weight acting downwards (200 g) * acceleration due to gravity (9.8 m/s^2) = 1.96 N (This force is neglected since it cancels out with the normal force)
- Thrust force or force from the plastic ball acting towards the right = ma (mass of the car * acceleration) = (200 g + 50 g) * 1.2 m/s^2 = 0.25 N
Free body diagram for the plastic ball:
- Weight acting downwards (50 g) * acceleration due to gravity (9.8 m/s^2) = 0.49 N (This force is neglected since it cancels out with the normal force)
- Reaction or normal force acting upwards = weight of the ball = 0.49 N
- Force from the car acting towards the left = force of the car's thrust = 0.25 N
(b) Action and reaction forces on each part of the toy:
- For the car, the action force is the thrust force exerted by the car on the plastic ball towards the right. The reaction force is the force exerted by the plastic ball on the car towards the left.
- For the plastic ball, the action force is the force exerted by the plastic ball on the car towards the left. The reaction force is the force exerted by the car on the plastic ball towards the right.
Note: In this case, there are no other forces considered since it was mentioned that there is negligible friction acting on each part of the toy.