Question

Conceptual questions of cars on the road.
a) When we see a car go by on the highway at 120 miles / h we exclaim things like "That car is really fast!", although in reality it is going with constant speed. Why if the accelerator pedal is too tight, the car is not accelerated? Explain using Newton's laws.
b) Many times we think that what makes the car move is its engine. However, no matter how powerful the motor (the energy it delivers per unit of time) is, the car cannot move if it is on a mudrack, or on a puddle of grease. Is it the engine, or is it the road that accelerates the car? Explain using Newton's laws.

Answer 1

1) Acceleration paddle is used to accelerate the car. The frictional force acts backward opposite to the direction of motion and acceleration paddle provides the force in forward direction so if Acceleration paddle us too tight so no force will be in forward direction and friction force will try to slow down the motion and eventually the car will get stopped.

2) For grease or mudtrack the frictional force is approximately zero. The frictional force is very necessary to move in forward direction since from Newton's III law every action have equal and opposite reaction so backward force provides forward force. If friction is not present so wheel will only rotate and not move forward.