Types of forces: at a distance or through contact (4841)

Indicate which of these phenomena are produced by forces at a distance and which are produced by forces through contact:

a) The motion of a train due to magnetic levitation.

b) The deformation of a spring when you attach a weight on it.

c) The skidding of a car on a pool of water.

d) The formation of the aurora borealis.

e) The motion of a cupboard when you push it.

Lengthen of a spring when a force is applied (4843)

A spring has an elastic constant of 120 N/m. Calculate how much it will lengthen by if a force of 35 N is applied.

Classification of bodies: rigid, elastic or plastic (4842)

Classify the following objects into rigid, plastic or elastic bodies:

a) The mechanism of a key of the computer keyboard.

b) Sunglasses.

c) A headband.

d) A steel fork.

e) The bristles of a toothbrush.

f) Bread dough.

Convertion of units: speed of a car (3600)

A car is moving in a straight path at 3 600 meters during 90 seconds. Determine the speed of the car, expressed in km/h.

Acceleration of a car (3583)

A car is increasing its speed from 40 m/s to 70 m/s. What is its acceleration if the time needed was 3 seconds?