1)A ball falls to the earth from a height h and bounces to a height h′. Momentum is conserved in the ball-earth system:
no matter what height h′ the ball reaches.
only if h′ < h.
only if h′ = h.
only if h′ > h.
only if h′≥ h.
2)A tap water pipe is bent as shown in the diagram. Sections 1 and 2 of the pipe are horizontal but section 2 is placed higher at a height of H. The diameter of the pipe of section 1 is?1.5 times larger than the diameter of section 2. Indicate which of the following is the most complete answer for the relationship between the hydrostatic pressures measured by the gauges in sections 1 and 2:
P1 < P2 because water flows slower in section 1.
P1 > P2 because water flows slower in section 1.
P1 > P2 because section 1 is lower than section 2.
P1 > P2 because water flows slower in section 1, and section 1 is lower than section 2.
For some value of H, P1 = P2 because the lower speed of the flowing water in section 1 is compensated by the hydrostatic pressure due to the difference H in the height of the two sections.
3)We know that a person emits about 500 W of radiation. We also know that a person sitting still uses about 100W of chemical energy. Where is the rest of the energy mainly coming from?
Heat conducted from the air into our body.
Convection of the heat.
Radiation from objects around us.
The energy, emitted by the body does not have to have a source.
Burning fat that we have accumulated previously.
4)In the two circuits shown above, the batteries are identical and maintain constant voltage. The light bulbs A, B, C and D, are identical and have resistance R. Assume that the bulbs are brighter when there is more current flowing through them. Which of the following relationships correctly describe the brightness of the bulbs?
A = B > C = D
C = D > A =B
A = B = C = D
A = C > B = D
5)The figure shows an accelerometer: a device for measuring the horizontal acceleration of cars and airplanes. The device consists of a ball that is free to roll on a parabolic track. A scale along the bottom is used to measure the ball’s horizontal position x. What is the acceleration of the car in m/s2?when the displacement of the ball in the accelerometer equals 0.20 m?