# A block is attached to a spring

A 15 kg block is firmly attached to a very light horizontal spring (k = 550 N/m) and resting on a smooth horizontal table. Suddenly it is struck horizontally by a 3 kg stone travelling with a velocity of 8 m/s to the right, whereupon the stone rebounds at 2 m/s to the left. Find the maximum distance that the block will compress the spring after the collision.

# Human-Powered Helicopter

A student builds a human-powered helicopter (HPH). It is a helicopter powered by one person carried on board and the power is generated by pedaling.
This human-powered helicopter has the following parameters: diameter of helicopter rotor blades is 15 meters and total mass is 100 kg. The air density 1.3 kg/m^3.

Can the HPH take off?

# Event violates the law of conservation …

The two toy cars have equal masses. The cars move towards each other at 0.5 m/s. They collide and bounce off each other at 1 m/s. This event violates the law of conservation of
a) mass
b) momentum
c) kinetic energy
d) potential energy
e) (b) and (c)
f) charge
g) all of these

# A cannon ball.

A cannon ball is fired vertically upward with an initial speed of Vo. At the highest point it explodes into two pieces of equal masses. One of the pieces hits the ground with a speed of 2Vo.
What is the speed of the second piece when it hits the ground?
How long was the second piece in the air?

# To what height does the m2 rebound ? The Collision problem.

A ball with small mass m2 placed on a ball with large mass m1. The bottom of the m1 is a height h above the ground and the bottom of the m2 is a height h + d above the ground. The balls are dropped. To what height does the m2 rebound?

Note. Please consider the balls are separated by a very small distance at the beginning, m1 is much larger than m2 and assume that the balls bounce elastically.

# Collision. Work. Power. Question 1

Question. Source. Yahoo ! Answers !

Issacs car collides with a stationary trolley . After the collision, the car and trolley lock together and move as one.mass of Issac’s car = 1700 kg
mass of trolley = 800 kg
Initial velocity of Issac’s car = 30 m s–11- Calculate the final velocity of the car and trolley together.
2- Mike’s car has a long crumple zone. Explain in detail why having this crumple zone would make a difference during impact. what are the ideas of velocity before and after the impact.

Issac’s car is towed away by a tow truck. The rope attached to the car makes an angle of 50 with the horizontal. The rope pulls the car with a force of 900N. The car moves a distance of 40 m along the horizontal road during a time of 20s.

3- What is the work done by the tow truck on the car.
4- What is the power produced by the tow truck while it is moving the car.

Solution.
1)
It is Perfectly inelastic collision .
M1*V1=(M1+M2)*UM1 – mass of Issac’s car
V1 – Initial velocity of Issac’s car
M2 – mass of trolley
U – final velocity of the car and trolley together1700*30=(1700+800)*U So, U = 20.4 m/s

2) than zone longer, Mike’s car safety

3)
W=F*D*COS (A)
W – work
F – force
D- distance
A – angle
W=900*40*COS(50)=23140.35 J

4)
P=W/t
P – Power
t – time
P=23140.35/20=1157.02 Watt