If you have a music CD collection of about 150 disks, estimate theorder of magni

Question

If you have a music CD collection of about 150 disks, estimate theorder of magnitude of the number of heartbeats you would have ifyou listened all the way through your collection. (a) 10^6 (b) 10^8(c) 10^10 (d) 10^4 (e) 10^3

A car and a truck, starting from rest, have the same acceleration,but the truck accelerates for twice the length of time. Compared with the car, the truck will travel (a) twice as far (b)three times as far (c) 1.4 times as far (d) four times as far (e)one half as far

An object is dropped from rest near the surface of the earth. If the time interval during which it falls is cut in half, thedistance it falls will (a) double (b) decrease by one-half (c)increase by a factor of four (d) decrease by a factor of four(e) not change

you drive for 30 mins at 100 km/h and then stop for 15 mins. youthen drive for 45 mins at 80 km/h. Your average speed for theentire trip is (a) 73 km/h (b) 83 km/h (c) 88km/h (d) 90 km/h (e)97 km/h

A baseball is thrown vertically up to a height of 30 m on theearth. If the same ball is thrown up on the moon with thesame initial speed how much farther will it travel up? (a)5.0 m (b) 25 m (c) 12m (d) 180 m (e) 150 m

A racecar starts from rest and accelarates at a constant rate andreaches a speed of 160 km/h (100 mph) in 6.0 s. It continuesat this speed for another 5 seconds. what is the car'saverage speed during the first 11 seconds? (a) 34.3 m/s (b) 29.3m/s (c) 22.2m/s (d) 32.3 m/s (e) 44.4 m/s

A sandbag is released from a rising air balloon and hits the ground7 seconds later. From what height was teh sandbag droppedfrom if at the moment of release the alloon was traveling upward at3 m/s? (a) 219 m (B) 240 m (C) 459 m (d) 261 m (e) 55m

The relationship between the velocity of a body moving alng the xaxis and time is given by v= 3t^2-2t, where the nits are SIunits.   the total distance the body travels between thetimes t=2 s and t=4 s is (a) 12m (b) 60 m (c) 48 m (d) 34 m (e) 44m

A river 1.00 mile wide flows with a constant speed of 1.00mi/h. A woman leaves from a point on the river bank. The woman rows a boat 1.00 miles directly upstream and returns tothe starting point. her speed in still water is 2.00 mi/h. The travel time for the woman is (a) 2.00 h (b) 1.15 h (c) 1.00h(d) 1.33 h (e) 0.67 h

An airplane flies 600 miles with a tailwind in 2.0 hrs. If it takes2.5 hrs to cover the same distance against the headwind, then whatis the speed of the plane in still air? (a) 270 mph (b) 300mph (c) 240 mph (d) 330 mph (e) 250 mph

Explanation / Answer

Wow - is that your entire assignment? :) Here's a hand with 1, 3 and 5 anyway. 1. (estimation) a CD last for 72min, that's ~10^2min. If you have150 (~10^2) then total listening time is 10^4 min. Finally a heartbeats at about 70bpm (~10^2 bpm) so total number of beats in10^4min is 10^6. 3. ball falling under gravity: only force is gravitational which isconstant with time (a=-9.8), so integrating that wrt time givesv=-9.8t+0 and integrating again gives vertical positiony=-4.9t^2+y_0 (y_0 is orig height). The important thing is that theposition changes with the square of time. So if time is halved, then change in position must bequartered. 5. throwing up ball on earth and moon: we're going to compare twosituations with diff gravitational accel so let's call themagnitude of the accel "a_g" and do the integration aspreviously: a(t)=-a_g v(t)=-a_g t + v_0 (v_0 is init speed when you throw it up, and issame on earth on and moon) y(t)=-a_g/2 t^2 + v_0 t + 0 (starting on the surface gives initialposition 0) You know that when the ball is at its maximum height, its velocitymust be 0, so we can work out the time it reaches v=0: v(t)=-a_g t+v_0=0 , rearrange for t: t=v_0/a_g And we know that when this occurs, its height is h_max: y(t=v_0/a_g)=-a_g(v_0/a_g)^2+v_0(v_0/a_g)=h_max so you need to do a bit of algebra and you'll have a neatexpression for h_max which most importantly contains a_g. What you should get is that h_max is inversely proportional to a_g.So if a_g goes down by a factor of 5 (or whatever it is for themoon!) and all other parameters remain constant, then h_max will goup by a factor of 5.

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