Venus is approximately a sphere of radius 6.06 10⁶ m.

(a) What is its circumference in kilometers?

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1 km
(b) What is its surface area in square kilometers?

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2 km²
(c) What is its volume in cubic kilometers?

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3 km³

Figure 2-42 shows a simple device for measuring your reaction time. It consists of a cardboard strip marked with a scale and two large dots. A friend holds the strip vertically, with thumb and forefinger at the upper dot and you position your thumb and forefinger at the lower dot, being careful not to touch the strip. Your friend releases the strip, and you try to pinch it as soon as possible after you see it begin to fall. The mark at the place where you pinch the strip gives your reaction time.

Figure 2-42

(a) How far from the lower dot should you place the 50.0 ms mark?

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1 cm ( = D₁)

(b) How much higher should the mark for 100 be? (For example, if the 100 ms marker should be two times as far from the dot as the 50 ms marker you would enter 2.)

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2D₁
How much higher should the mark for 150 be?

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3D₁
How much higher should the mark for 200 be?

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4D₁
How much higher should the mark for 250 be?

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5D₁

Two blocks are in contact on a frictionless table. A horizontal force is applied to one block, as shown in Fig. 3-36.

Figure 3-36

(a) If m₁ = 2.8 kg, m₂ = 1.1 kg, and F = 3.7 N, find the force between the two blocks.

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1 N
(b) If a force of the same magnitude F is applied to m₂ but in the opposite direction, what is the force between the blocks? It is not the same value calculated in (a).

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2 N

(c) Explain the difference.
3

A 5.00 kg block is pulled along a horizontal frictionless floor by a cord that exerts a force F = 14.0 N at an angle = 25.0° above the horizontal, as shown in Fig. 4-29.

Figure 4-29

(a) What is the magnitude of the acceleration of the block?

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1 m/s²
(b) The force F is slowly increased. What is its value just before the block is lifted (completely) off the floor?

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2 N
(c) What is the magnitude of the acceleration of the block just before it is lifted (completely) off the floor?

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3 m/s²

A horizontal force F of 17 N pushes a block weighing 6.0 N against a vertical wall (Fig. 5-47). The coefficient of static friction between the wall and the block is 0.63 and the coefficient of kinetic friction is 0.43. Assume that the block is not moving initially.

Figure 5-47

(a) Will the block start moving?

1

no yes    

(b) In unit-vector notation, what is the force exerted on the block by the wall?

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2 i N +

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3 j N