According to Newton's law of inertia, a railroad train in motion should continue going forever even if its engine is turned off. We never observe this because railroad trains
A) move too slowly.
B) are much too heavy.
C) must go up and down hills.
D) always have forces that oppose their motion.
Answer: D
Learn More :
Physics
- A 400 kg vehicle is travelling in outer space at a speed of 200 m/s. The smallest constant force that must be applied to stop it in 20 seconds is
- A skydiver falls towards the Earth. The attraction of the Earth on the diver pulls the diver down. What is the reaction to this force?
- A baseball player bats a ball with a force of 1000 N. The reaction force that the ball exerts against the bat is
- Two people, one twice as massive as the other, attempt a tug-of-war with 12 meters of massless rope on frictionless ice. After a brief time, they meet. The heavier person slides a distance of
- An archer shoots an arrow. Consider the action force to be the bowstring against the arrow. The reaction to this force is the
- Wherever there is an action force, there must be a reaction force that
- A feather and a coin will have equal accelerations when falling in a vacuum because
- A skydiver, who weighs 500 N, reaches terminal velocity of 90 km/h. The air resistance on the diver is then
- If more horizontal force is applied to a sliding object than is needed to maintain a constant velocity
- If an object of constant mass experiences a constant net force, it will have a constant
- A 2000-kg car experiences a braking force of 8,000 N and skids to a stop in 5 seconds. The speed of the car just before the brakes were applied was
- If you are driving at 20 m/s and slam on your brakes and skid at 0.5 g to a full stop, the skidding time in seconds is
- A skydiver of mass 100 kg experiences air resistance of 600 N, and an acceleration of
- A 1-kg ball is thrown at 10 m/s straight upward. Neglecting air resistance, the net force that acts on the stone when it is halfway to the top of its path is about
- Suppose a particle is being accelerated through space by a 10-N force. Suddenly the particle encounters a second force of 10 N in the opposite direction from the first force. The particle with both forces acting on it
- A 10-N block and a 1-N block lie on a horizontal frictionless table. To provide them with equal horizontal acceleration, we would have to push with
- A bag of groceries has a mass of 10 kilograms and a weight of
- A bag of groceries has a mass of 10 kilograms and a weight of
- A car has a mass of 1000 kg and accelerates at 2 meters per second per second. What is the magnitude of the net force exerted on the car?
- A heavy block at rest is suspended by a vertical rope. When the block is accelerated upward by the rope, the rope tension
- Which has zero acceleration? An object
- An apple weighs 1 N. When held at rest above your head, the net force on the apple is
- An object is pulled northward by a force of 10 N and at the same time another force of 15 N pulls it southward. The magnitude of the resultant force on the object is
- If an object's mass is decreasing while a constant force is applied to the object, the acceleration
- A 10-kg brick and a 1-kg book are dropped in a vacuum. The force of gravity on the 10-kg brick is