PHY203F08 Exam 2 Name: __________________________

1.	A shopper steps on an escalator moving downward at a constant speed toward the bargain basement in a large department store. On his way down, the normal force exerted on him by the step of the escalator is
	A)	greater than his weight when he is off the escalator.
	B)	equal to his weight when he is off the escalator.
	C)	less than his weight when he is off the escalator.
	D)	dependent on how fast the escalator is moving.
	E)	unknown; insufficient information is given to answer correctly.

2.	A particle of mass 1.3 kg is sliding down a frictionless slope inclined at 30º to the horizontal. The acceleration of the particle down the slope is
	A) 4.9 m/s^2 B) 9.8 m/s^2 C) 0.5 m/s^2 D) 8.5 m/s^2 E) 1.3 m/s^2

3.	A body is sent out in space. Which of the following statements is true of this body as it moves away from Earth?
	A)	The body's mass and weight remain equal.
	B)	The body's mass and weight decrease.
	C)	The body's mass decreases, and its weight remains constant.
	D)	The body's mass remains constant, and its weight decreases.
	E)	The body's mass decreases, and its weight increases.

4.	A block of mass m is at rest on an inclined plane that makes an angle of 30º with the horizontal, as shown in the figure. Which of the following statements about the force of static friction is true?
	A)	fs > mg	D)	fs = mg sin 30º
	B)	fs > mg cos 30º	E)	None of these statements is true.
	C)	fs = mg cos 30º

5.	A particle is moving uniformly in a circle with radius 50 cm. The speed of the particle is 60 cm/s. The acceleration of the particle has a magnitude of
	A) zero B) 36 m/s^2 C) 1.8 ´ 10^5 cm/s^2 D) 72 cm/s^2 E) 3.6 m/s^2

6.	Three blocks are connected by massless cords and hung by a third massless cord to a beam. Mass m1 = 2 m2 = 3 m3. Mass m1 is the lowest block and m3 is the highest. The tension in the cord between the two highest blocks is
	A) m1g/2 B) 3m1g/2 C) m1g/6 D) 2m1g/3 E) 6m1g/11
7.	The kinetic energy of a car is 1.00 ´ 10^5 J. If the car's speed is increased by 20.0 percent, the kinetic energy of the car becomes
	A)	1.44 ´ 10^5 J
	B)	1.20 ´ 10^5 J
	C)	4.00 ´ 10^5 J
	D)	1.04 ´ 10^5 J
	E)	unknown; the answer depends on the mass of the car, which is not given

8.	A constant force of 45 N directed at angle q to the horizontal pulls a crate of weight 100 N from one end of a room to another a distance of 4 m. Given that the vertical component of the pulling force is 12 N, calculate the work done by the force in moving the crate.
	A) 4.1 ´ 10^2 J B) 48.0 J C) 3.9 ´ 10^2 N/m D) 1.7 ´ 10^2 J E) 3.9 ´ 10^3 J

9.	What is the work done by a car's braking system when it slows the 1500-kg car from an initial speed of 96 m/s down to 56 m/s in a distance of 55 m?
	A) 8.3 kJ B) 20 kJ C) 4.6 MJ D) 2.5 MJ E) 8.3 MJ

10.	Power P is required to lift a body a distance d at a constant speed v. What power is required to lift the body a distance 2d at constant speed 3v?
	A) P B) 2P C) 3P D) 6P E) 3P/2

11.

A donkey is attached by a rope to a wooden cart at an angle of 23.0° to the horizontal, that is, a slight upward pull on the cart. The tension in the rope is 210 N. The cart is dragged horizontally along the floor with a constant speed of 6 km/h. The coefficient of kinetic friction is 0.300. A) Draw a free body diagram of the cart showing all forces (clearly labeled). B) Find the horizontal (x) component of the force applied to the cart by the donkey. C) Find the vertical (y) component of the force applied to the cart by the donkey. D) Calculate how much work the donkey does in 35 minutes. E) Find the power delivered to the cart by the donkey.

12.

A 5.00-kg blob of putty is dropped from a height of 10.0 m above the ground onto a light vertical spring the top of which is 5.00 m above the ground. The spring constant k = 200 N/m and the blob compresses (maximally) the spring by 1.50 m. A) Taking gravitational potential energy to be zero at the ground, find the potential energy of the putty initially. B) Find the gravitational potential energy of the putty at maximal compression of the spring. C) Find the kinetic energy of the putty at maximal spring compression. D) Find the elastic energy at maximal compression. E) With mechanical energy loss going into thermal, find the amount of thermal energy generated.