### Newton : Tut 1

**1.** An object of mass 12kg is placed on a horizontal, frictionless surface.
A force of 36N is exerted on the object for a certain period of time. The velocity of the object
becomes 60ms^{-1} at the end of this time. The force is then removed.

**1.1.** Calculate the duration for which the force was acting.

**1.2.** Describe the motion of the object after the force was
removed.

The object would continue moving at a constant velocity of 60m.s^{-1}.

All horizontal forces are removed (no friction as well).

According to N(I), as a result of it's inertia, the object must maintain the constant velocity.

**2.** A 3kg cart moving rightwards, is brought to rest from an
initial velocity of 18m.s^{-1} in 12s by the action of friction between the wheels and the ground.

**2.1.** Draw the cart and show and label all the forces acting on the cart.

**2.2.** Calculate the acceleration of the cart.

**2.3.** Calculate the frictional force.

**3.** A cyclist is riding a bicycle of 20kg at a constant velocity of 6,4m.s^{-1}. He then applies a constant force of magnitude 80N with the brakes,
thus bringing the bicycle to a halt in 4s.

**3.1.** Calculate the acceleration of the cyclist.

**3.2.** Calculate the mass of the cyclist.

**4.** A motorist is traveling in a vehicle of mass 1200kg at a velocity
of 118,8km/h. He then notices that he is 85m away from an 80km/h zone.
He presses the brake pedal which produces a constant force of magnitude 3600N to the wheels.

Prove that he does not reduce the speed to the required limit.

**5.** A cart of mass 280kg is pulled by a horse from rest, to a speed of 36km/h in 5s.
Calculate the force exerted by the horse if 20% of the applied force was used to overcome friction.