# Can you help with my physics homework? ?

1. A bicycle initially at rest accelerates for t = 16.5 seconds at a rate of a = 1.5 m/s2.

1. A)Calculate the distance in meters traveled by this bike.1. B)  Enter an expression, in terms of defined quantities, for the final velocity of the bicycle after time t. 1. C) Calculate the final speed, in meters per second. 2. Two cars both cover a straight distance, d = 257 m, in time t = 16 s. Car A moves at a constant velocity (vA). Car B moves at a constant acceleration (aB), starting from an initial velocity of v0B = 8.5 m/s. Assume both cars are moving in the positive x-direction.2. A) What is the velocity of car a?2. B) What is the final velocity of car b?2. C) What is the acceleration of car b?3. A bullet is shot straight up into the air from ground level. It reaches a maximum height at h = 713 m.3. A) Calculate initial speed of bullet in m/s3. B) Calculate the total flight time in seconds until the bullet reaches the ground

Relevance
• Who is riding this bike?  90 km/hr is a ridiculous speed for a cyclist.  If you exclude wind resistance the person needs an average of 1.8 kW and a peak of 3.6 kW to get to this speed in the time.  Adding wind resistance it is over 5 kW .  Other than superman who can do this?

• 1. A bicycle initially at rest accelerates for t = 16.5 seconds at a rate of a = 1.5 m/s2.

1. A)Calculate the distance d in meters traveled by this bike.

d = Vo*t+a/2*t^2 = 0*15+1.5/2*16.5^2 = 204 m

1. B) Enter an expression, in terms of defined quantities, for the final velocity Vf of the bicycle after time t.

Vf = a*t = 1.5t m/sec

1. C) Calculate the final speed Vf in meters per second.

Vf = 1.5*16.5 = 24,8 m/sec

2. Two cars both cover a straight distance, d = 257 m, in time t = 16 s. Car A moves at a constant velocity (Va). Car B moves at a constant acceleration (ab), starting from an initial velocity Vob = 8.5 m/s. Assume both cars are moving in the positive x-direction.

2. A) What is the velocity Va of car a?

Va = d/t = 257/16 = 16.1 m/sec

2. B) What is the final velocity Vb  of car b?

d = Vob*t+a/2*t^2

257 = 8.5*16+a/2*16^2

ab = ( 257 - 8.5*16)*2/16^2 = 0.95 m/sec^2

Vb = Vob+ab*t = 8.5+0.95*16 = 23.7 m/sec

check : (23.7+8.5)*16/2 = 257 m   OK !!!

2. C) What is the acceleration ab of car b?

ab = ( 257 - 8.5*16)*2/16^2 = 0.95 m/sec^2

3. A bullet is shot straight up into the air from ground level. It reaches a maximum height at h = 713 m.

3. A) Calculate initial speed Vo of bullet in m/s

conservation of energy shall apply  :

Vo = √ 2gh = √ 19.614*713 = 118.3 m/sec

3. B) Calculate the total flight time t in seconds until the bullet reaches the ground

t = 2*Vo/g = 2*118.3/9.807 = 24.1 sec 