1. Find the height from which you would have to drop a ball so that it would hav

Question

1. Find the height from which you would have to drop a ball so that it would have a speed of 7.6 m/s just before it hits the ground.
1. m

2. A child and sled with a combined mass of 50.2 kg slide down a frictionless hill that is 8.14 m high. If the sled starts from rest, what is its speed at the bottom of the hill?
1. m/s

3. A 50 kg pole vaulter running at 10 m/s vaults over the bar. Her speed when she is above the bar is 1.3 m/s. Neglect air resistance, as well as any energy absorbed by the pole, and determine her altitude as she crosses the bar.
1. m

4. A 0.700 kg bead slides on a curved wire, starting from rest at point A in Figure P5.28.point A is 5.00m, point B is ground level, point C is 2.00m above ground. If the wire is frictionless, find each of the following.
(a) the speed of the bead at B
1. m/s
(b) the speed at C
2. m/s


5. A spring has a force constant of 480.0 N/m.
(a) Determine the potential energy stored in the spring when the spring is stretched 3.81 cm from equilibrium.
1. J
(b) Determine the potential energy stored in the spring when the spring is stretched 3.18 cm from equilibrium.
2. J
(c) Determine the potential energy stored in the spring when the spring is unstretched.
3. J

6. A 0.190 kg block on a vertical spring with spring constant of 4.65 103 N/m is pushed downward, compressing the spring 0.099 m. When released, the block leaves the spring and travels upward vertically. How high does it rise above the point of release?
1. m

Explanation / Answer

Use conservation of energy: PE=KE mgh=1/2mv^2 masses cancel gh=1/2v^2 We want the height: h=(1/2v^2)/g We want a speed of 7.6 m/s h=(1/2(7.6)^2)/9.8 h=2.95m

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